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Understanding measurement conversion is crucial in various fields, from engineering to daily life. The lesson emphasizes the importance of being proficient in converting units, especially within the metric system. It also delves into the concept of unit ratios, illustrating their practical applications like determining speed or converting dimensions of objects. This knowledge serves as a comprehensive guide for those involved in activities that require a nuanced understanding of unit conversions, making it easier to meet specific criteria or standards.
| Student Learning Objectives: |
|---|
|
| | 14 Theory slides |
| | 10 Exercises - Grade E - A |
| | Each lesson is meant to take 1-2 classroom sessions |
Ignacio and Emily are competing in an international remote control car race.
Ignacio car traveled 0.4 miles in 2 hours. Emily's car traveled at an average speed of 0.4 kilometers per hour. Whose car drove at a higher average speed?
A unit ratio is a ratio with a denominator of 1 unit.
When writing unit ratios using different units of measure, the denominator of the unit ratio is still 1 unit. Note that different ratios can be written using the same relationships.
| Fact | 1 foot is equal to 12 inches. | 1 hour is equal to 60 minutes. |
|---|---|---|
| Ratio | 1ft/12in. | 1h/60min |
The denominators of these ratios are different than 1 unit. Dividing both the numerator and denominator of each ratio by the number in the denominator will give the appropriate unit ratio.
Write the given ratio in the indicated form. Do not round any decimal numbers.
Ignacio found a map of his school's campus.
a*b/c= a* b/c
Cross out common units
Cancel out common units
Multiply
a/1=a
This means that 1.4 inches on the map represents 0.105 miles in real life.
A conversion factor is a fraction where the numerator and denominator represent the same quantity with different units. Example Conversion Factor [0.5em] 60 minutes/1 hour Recall that 1 hour and 60 minutes represent the same quantity. Multiplying a quantity by a conversion factor changes the quantity to an equivalent quantity in different units.
| Given Quantity | Conversion | Result |
|---|---|---|
| 2 hours | 2 hours * 60 minutes/1 hour | 120 minutes |
The process of including units of measurement as factors is called dimensional analysis. Dimensional analysis can also be used when deciding which conversion factor will produce the target units.
The customary system is the measurement system most commonly used in the United States. This system of measurement contains units for length, capacity, and weight. For example, the inch is a unit of length, the ounce is a unit of weight, and the quart is a unit of volume. Examples of Units in the Customary System inch, ounce, and quart The table shows the relationship between units of each measure type in the customary system.
| Customary Units | ||
|---|---|---|
| Type | Unit | Equivalent Unit |
| Length | 1 foot (ft) | 12 inches (in.) |
| 1 yard (yd) | 3ft | |
| 1 mile (mi) | 5280ft | |
| Weight | 1 pound (lb) | 16 ounces (oz) |
| 1 ton (T) | 2000 lb | |
| Volume | 1 cup (c) | 8 fluid ounces (fl oz) |
| 1 pint (pt) | 2c | |
| 1 quart (qt) | 2pt | |
| 1 gallon (gal) | 4qt | |
Remote control cars in a robotics competition must weigh less than 6 pounds. Tearrik's car currently weighs 84 ounces.
Find the weight of the car in pounds.
Does the weight of this robotic car meet the requirement?
Write a conversion factor using the fact that 1 pound is 16 ounces.
Is the answer from Part A less than 6 pounds?
To convert the weight of the remote control car from ounces to pounds, we can use a conversion factor. Let’s first recall that 1 pound is 16 ounces.
1lb = 16oz Since our target unit is pounds, it goes in the numerator of the conversion factor. The denominator will have the same unit as the given amount, ounces, so the units cancel out. Conversion Factor Ounces → Pounds [0.8em] 1 lb/16 oz Now we can use this conversion factor to write 84 ounces in pounds.
a*b/c= a* b/c
Cross out common units
Cancel out common units
a * 1=a
a* b/c=a/c* b
Calculate quotient
Tearrik's car weighs 5.25 pounds.
We found that Tearrik's car weighs 5.25 pounds, which is less than the competition's maximum weight of 6 pounds. This means that Tearrik's car meets the weight requirement.
The metric system is a measurement system commonly in most countries around the world. The base units in the metric system are meters for length, liters for capacity, and kilograms for weight. Base Units in Metric System meter, liter, and kilogram In the metric system, units are related by powers of 10. Metric units are named by adding metric prefixes to the base units.
The table shows the commonly used metric units of length.
| Unit | Equivalent Unit |
|---|---|
| 1000 millimeters (mm) | 1 meter (m) |
| 100 centimeters (cm) | 1m |
| 10 decimeters (dm) | 1m |
| 1 dekameter (dam) | 10m |
| 1 hectometer (hm) | 100m |
| 1 kilometer (km) | 1000m |
For measuring capacity, the metric system uses the liter as the base unit.
| Unit | Equivalent Unit |
|---|---|
| 1000 milliliters (mL) | 1 liter (L) |
| 100 centiliters (cL) | 1L |
| 10 deciliters (dL) | 1L |
| 1 dekaliter (daL) | 10L |
| 1 hectoliter (hL) | 100L |
| 1 kiloliter (kL) | 1000L |
In the metric system, kilogram, gram, and milligram are some commonly used units for measuring weight.
| Unit | Equivalent Unit |
|---|---|
| 1000 milligrams (mg) | 1 gram (g) |
| 100 centigrams (cg) | 1g |
| 10 decigrams (dg) | 1g |
| 1 dekagram (dag) | 10g |
| 1 hectogram (hg) | 100g |
| 1 kilogram (kg) | 1000g |
Remote control cars in a robotics competition must be no longer than 40 centimeters.
Emily's car is 0.35 meters long. Write this length in centimeters.
Does this car meet the length criteria?
Write a conversion factor using the fact that 1 meter is 100 centimeters.
Is the answer from Part A longer than 40 centimeters?
To convert the given length from meters to centimeters, we can use a conversion factor. Let's first recall that 1 meter is 100 centimeters.
1m = 100 cm Since the target unit is centimeters, we will put 100cm in the numerator of the conversion factor. The denominator will contain its equivalent length, 1m. 100cm/1m Now we can convert the given quantity from meters to centimeters by multiplying it by this conversion factor.
a*b/c= a* b/c
Cross out common units
Cancel out common units
a/1=a
Multiply
The length of the car is 35 centimeters.
Emily's car is 35 centimeters long, which is less than 40 centimeters, so her car meets the competition's length requirement.
Units can be converted between the customary system and the metric system using conversion factors. Use the applet below to explore several common conversion factors.
Fill in the table to convert between units.
| Applications | ||||
|---|---|---|---|---|
| Car | Weight | Length | ||
| Car 1 | 5.3 pounds | A kilograms | 15 inches | B centimeters |
| Car 2 | C pounds | 2.5 kilograms | D inches | 35 centimeters |
If necessary, round answers to the nearest tenth.
The weights are in kilograms and pounds. Let's recall that 1 kilogram is about 2.2 pounds. We can create a conversion factor using this information.
Car 1 weighs 5.25 pounds, so our conversion factor should have a numerator in kilograms and a denominator in pounds. 1kg/2.2lb Now we can multiply the weight of Car 1 by this conversion factor.
a*b/c= a* b/c
Cross out common units
Cancel out common units
a * 1=a
a* b/c=a/c* b
Calculate quotient
Round to 1 decimal place(s)
Car 1 weighs about 2.4 kilograms, so the value of A is 2.4.
Now we want to convert the weight of Car 2 from kilograms to pounds, so we can use the multiplicative inverse of the previous conversion factor. 2.2lb/1kg Let's use this factor to find the equivalent weight in pounds.
a*b/c= a* b/c
Cross out common units
Cancel out common units
a/1=a
Multiply
Car 2 weighs 5.5 pounds, so the value of C is 5.5.
This part requires converting between inches and centimeters. Let's remember that 1 inch is 2.54 centimeters.
Car 1 is 15 inches long. To convert this length to centimeters, we can use the following conversion factor. 2.54cm/1in. Now we can multiply the given length by this conversion factor to find its equivalent length in centimeters.
a*b/c= a* b/c
Cross out common units
Cancel out common units
a/1=a
Multiply
Car 1 is 38.1 centimeters long, so the value of B is 38.1.
Lastly, we convert the length of Car 2 from centimeters to inches. To do this, we multiply 35 cm by 1 in. 2.54cm.
a*b/c= a* b/c
Cross out common units
Cancel out common units
a * 1=a
a* b/c=a/c* b
Calculate quotient
Round to 1 decimal place(s)
Car 2 is about 13.8 inches long, so D is 13.8. Let's fill in the table with our findings.
| Applications | ||||
|---|---|---|---|---|
| Car | Weight | Length | ||
| Car 1 | 5.3 pounds | 2.4 kilograms | 15 inches | 38.1 centimeters |
| Car 2 | 5.5 pounds | 2.5 kilograms | 13.8 inches | 35 centimeters |
Two remote control cars race around a 80-foot track.
Car A completed one lap in 5 minutes. Find the speed of the car in inches per second.
Car B completed 3 laps in 16 minutes. Find the speed of the vehicle in centimeters per second.
Which car will likely win?
The speed of an object is the distance traveled divided by the time elapsed. Remember that 1 foot is 12 inches.
Keep in mind that 1 foot is 30.48 centimeters.
Determine how many feet each car travels in one minute.
The speed of an object is calculated by dividing the distance traveled by the amount of time spent traveling. Since one lap is 80 feet and Car A completes a lap in 5 minutes, we can write its speed as follows.
r = 80 ft/5min Notice that this unit is feet per minute. To convert this to inches per second, we need to combine two conversion factors.
| Equivalent Quantities | Conversion Factor |
|---|---|
| 1 ft = 12 in. | 12 in./1ft |
| 1 min = 60 sec | 1 min/60sec |
Let's multiply the speed by the conversion factors.
Multiply fractions
Cross out common units
Cancel out common units
a * 1=a
Multiply
Calculate quotient
The speed of the car is 3.2 inches per second.
Car B completed 3 laps in 16 minutes. Since one lap is 80 feet, 3 laps is equal to 240 feet. We can use this information to find the speed of the car in feet per minute.
r = 240 ft/16min To convert it to centimeters per second, we need two conversion factors.
| Equivalent Quantities | Conversion Factor |
|---|---|
| 1 ft = 30.48 cm | 30.48 cm/1ft |
| 1 min = 60 sec | 1 min/60sec |
Again, we multiply the speed by the conversion factors.
Multiply fractions
Cross out common units
Cancel out common units
a * 1=a
Multiply
Calculate quotient
Car B travels at a speed of 7.62 centimeters per second.
To find which car is more likely to win the race, we can compare their speeds. Let's use the speeds in feet per minute that we found in the previous parts.
| Car A | Car B | |
|---|---|---|
| Speed = Distance/Time | 80 ft/5min | 240 ft/16min |
| Simplify | 16ft/min | 15ft/min |
Car A is faster, so it is more likely to win the race.
| Car A | Car B | |
|---|---|---|
| Speed | 3.2in./sec | 7.62cm/sec |
To compare these quantities, let's use the fact that 1 inch is 2.54 centimeters. We will multiply the speed of Car A by 2.54 cm1 in. to convert it to centimeters per second. 3.2in./1 sec * 2.54 cm/1 in. = 8.128cm/1 sec Car A travels at 8.128 centimeters per second, which is greater than Car B's speed of 7.62 centimeters per second.
Earlier we were given the distance traveled by two different remote control cars.
| Travels | |
|---|---|
| Ignacio's Car | 0.4 miles in 2 hours |
| Emily's Car | 0.4 kilometers per hour |
Since speed is distance traveled divided by time, the speed of Ignacio's car is 0.4 miles divided by 2 hours. Ignacio's Car [0.7em] 0.4 miles/2 hours = 0.2miles/1 hour Ignacio's car travels at 0.2 miles per hour. Emily's car's speed is given in kilometers per hour, however. To compare two speeds with different units, one of them must be rewritten in terms of the other. Let's use the conversion factor between kilometers and miles. 1mile is about1.6kilometers. ⇓ Conversion Factor 1 mi/1.6 km Use this factor to convert kilometers per hour to miles per hour.
Multiply fractions
Cross out common units
Cancel out common units
a * 1=a
a/b=.a /1.6./.b /1.6.
Round to 1 decimal place(s)
An electric car factory plans to make its new models 39 inches wide.
How wide are the new models in feet?
We want to determine how wide the new models are in feet. To do so, we first need to recall the measures of length in the customary system, and the relationships between them.
We can see the relationship between feet and inches in the first row. We will now write a conversion factor for these units. Since we want to convert inches into feet, our ratio will have inches in the denominator. We need to write 1 foot in the numerator and 12 inches in the denominator. Conversion Factor 1ft/12in. To find the width of the electric vehicle in feet, we need to multiply the given width, 39 inches, by the conversion factor. We will start with writing the product. Then, we will cancel out the common units. This will give us the desired unit, feet.
New model cars will be 3.25 feet wide.
The speed of light is about 300 000 kilometers per second. The Sun is about 142 million miles away from Mars. How many minutes does it take for sunlight to reach Mars? Round the answer to the nearest integer.
Consider that the speed of light is about 300 000 kilometers per second. We can write it as a fraction. 300 000kilometers per second ⇓ 300 000 km/1 sec We know that the Sun is about 142 million miles away from Mars. We want to determine the amount of time it takes for sunlight to reach Mars. To do so, we will start by converting the Sun's distance from miles to kilometers using the fact that 1 mile is about 1.61 kilometers. Conversion Factor 1.61 km/1 mi Let's multiply this factor by 142 million miles to convert from miles to kilometers.
This means that the Sun is about 228 620 000 kilometers from Mars. Now that we have the distance in kilometers, we can divide it by 300 000 kilometers per second to obtain the number of seconds it will take for sunlight to reach Mars.
It takes about 762 seconds for sunlight to reach Mars. Recall that 1 minute is equal to 60 seconds. Then, we can use this information as a conversion factor. 1min/60sec Now, let's multiply this conversion factor by 762 seconds.
Therefore, it takes about 13 minutes for sunlight to reach Mars.
Magdalena is doubling a recipe for a homemade cleaning solution. The new recipe calls for 12 cups of vinegar. Magdalena converts it to pints in the following way.
Determine which of the given sentences about Magdalena's calculations are correct.
It is a given that Magdalena tried to convert 12 cups to pints. 12 c= pt Magdalena multiplies 12 cups by the conversion factor 2 cups1 pint, and she gets 24 pints.
It turns out that she has made some errors. Let's describe those errors.
The correct conversion factor, in this case, is the reciprocal of 2 cups1 pint, which is 1 pint2 cups. Conversion Factor 1 pt2 c We can conclude that statements I and III are correct. We can perform the conversion correctly by using the factor we wrote.
We showed that 12 cups is 6 pints.
At a restaurant, a chef uses 14 pounds of butter every day. How many grams of butter does the chef use every day?
Use the conversion factors 16 ounces1pound and 28.35 grams1ounce.
We know a chef uses 14 pounds of butter every day. We want to find out how many grams of butter that is. We are given two conversion factors.
| Conversion Factors | |
|---|---|
| From Pounds to Ounces | 16ounces/1pound |
| From Ounces to Grams | 28.35grams/1ounce |
Using the given conversion factors, we can write the conversion factor we need. When we multiply the conversion factors, the ounces measurement will cancel each other out.
We can use this factor to convert from pounds to grams. Let's do it!
We found that 14 pounds is 6350.4 grams. This means that the chef uses 6350.4 grams of butter every day.