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| 11 Theory slides |
| 10 Exercises - Grade E - A |
| Each lesson is meant to take 1-2 classroom sessions |
Here are a few recommended readings before getting started with this lesson.
A ratio is a comparison of two quantities that describes how much of one thing there is compared to another. Ratios are commonly represented using colon notation or as fractions. They are read as the ratio of a to b,
where b is a non-zero number.
Fraction Form | Greatest Common Factor | Rewrite | Simplify | |
---|---|---|---|---|
Tearrik | 1527 | GCF(27,15)=3 | 5⋅39⋅3 | 59 |
Zain | 2545 | GCF(45,25)=5 | 5⋅59⋅5 | 59 |
Scaling is a way of creating equivalent ratios by multiplying or dividing the numerator and denominator of a ratio by the same number. Sometimes it is necessary to scale back and forward to find an equivalent ratio for a particular situation. Consider the following scenario.
Chocolate bars are on sale at 14 for $6. This ratio can be scaled up and down to find the cost of 21 chocolate bars.
614 | |
---|---|
Scaling Back | Scaling Forward |
6÷214÷2 | 3×37×3 |
37 | 921 |
Determine whether the given pair of ratios is equivalent.
Mark loves taking pictures with his camera. One of his favorite shots is of the Walter Pyramid. The picture has a height-to-width ratio of 3:4.
He wants to print it out and hang it on his bedroom wall, but he wants to print it in two different sizes equivalent to the original one.
Tables of equivalent ratios are called ratio tables. Consider the ratio table containing the distance Zain runs and the time it takes him to cover that distance.
Distance Run (Miles) | 1 | 2 | 3 | 4 |
---|---|---|---|---|
Time (Minutes) | 10 | 20 | 30 | 40 |
The ratios 101, 202, 303, and 404 are equivalent since each of them simplifies to a ratio of 101. A ratio table can be created by multiplying or dividing each quantity in a ratio by the same number, or by repeatedly adding or subtracting the ratio.
Mark received a new phone from his parents that has an excellent camera for his photography hobby.
The aspect ratio, which represents the relationship between height and width, of the main camera is 2:3. Mark created a ratio table to explore the equivalent ratios that his photos can have.
Height | 2 | A | 6 | 18 |
---|---|---|---|---|
Width | 3 | 6 | 9 | B |
However, the table is missing some values.
Height | 2 | A | 6 | 18 |
---|---|---|---|---|
Width | 3 | 6 | 9 | B |
Use the initial ratio of 2:3 to determine the ratio for the second column. Note that adding 3 to the width of the first ratio gives 6. This means that 2 can be added to the height of the first ratio to find the height that corresponds to a width of 6, which is the value of A.
Use the ratio of 6:9 to determine the corresponding width for a height of 18. Since 6⋅3=18, multiply 9 by 3 to get the value of B.
Therefore, A=4 and B=27.
Height, x | 2 | 4 | 6 | 18 |
---|---|---|---|---|
Width, y | 3 | 6 | 9 | 27 |
Because the table contains only positive values, only the first quadrant is required. Begin at the origin and move along the x-axis according to the number of units specified by the height. Then, move vertically the number of units specified by the width to graph each ratio.
This graph corresponds to option A.
Mark and Maya met up to compare the results of a five-day photo challenge. They each recorded the total number photos taken on each day in a table so that they could make a collage after finishing the challenge. The following table shows the data recorded by Maya and Mark.
Maya | Mark | ||
---|---|---|---|
Days | Photos | Days | Photos |
1 | 5 | 1 | 7 |
2 | 10 | 2 | 14 |
3 | 15 | 3 | 21 |
4 | 20 | 4 | 28 |
5 | 25 | 5 | 35 |
Maya | ||
---|---|---|
Days | Photos | (x,y) |
1 | 5 | (1,5) |
2 | 10 | (2,10) |
3 | 15 | (3,15) |
4 | 20 | (4,20) |
5 | 25 | (5,25) |
To graph the data, begin at the origin and move along the x-axis the number of units specified by the day. Then, move the number of units specified by the photos taken vertically to graph each ordered pair.
Before adding Mark's data to the graph, write each column of the table as an ordered pair.
Mark | ||
---|---|---|
Days | Photos | (x,y) |
1 | 7 | (1,7) |
2 | 14 | (2,14) |
3 | 21 | (3,21) |
4 | 28 | (4,28) |
5 | 35 | (5,35) |
Each ordered pair can now be added to the graph.
The graph corresponds to the one given in option B.
Maya | Mark | |
---|---|---|
Day, x | 1 | 1 |
Photos, y | 5 | 7 |
Maya's photo-to-day ratio is 5:1 and Mark's is 7:1. Now, look at the graph drawn in Part A.
Notice that both sets of points appear to fit in straight lines. However, the line for Mark is steeper than the line for Maya. The statements that are true about the ratios of photos taken to days passed have been identified.
Statement | True? |
---|---|
The ratio of photos to days for Maya is 5:1. | ✓ |
The ratio of photos to days for Mark is 7:1. | ✓ |
The line for Mark's data is steeper than the line for Maya's. | ✓ |
The ratio of days to photos for Maya is 5:1. | × |
The ratio of days to photos for Mark is 7:1. | × |
The line for Maya's data is steeper than the line for Mark's. | × |
Maya suggested Mark post his outstanding artwork on a website for people to buy. As a beginner seller, Mark received a graph that showed how much he would earn per photo sold.
Use the relationship between a pair of consecutive points on the graph to determine the ratio of money earned to photos sold. Apply that ratio to find the point for selling six photos on the graph.
Mark wants to know how much money he would earn for selling six photos. It is given that the ratio of money earned per photo sold remains constant. Consider the graph carefully. The points appear to fall in a straight line.
The point (4,6) is 2 units to the right and 3 units up from point (2,3).
This means that the ratio of the money earned to photos sold is 3:2 — Mark will earn $3 for every 2 photos sold. The amount of money he will earn by selling six photos can be determined using this ratio. Move 2 units to the right and 3 units up from (4,2) to locate this point.
Therefore, Mark would earn $9 for selling six photos.
This lesson covered some uses of equivalent ratios and how ratio tables can be used to find them. Equivalent ratios are particularly useful when scaling ratios to maintain proportions. Take a look at a ratio table that shows how many photos Maya's printer can print per minute.
Photos | 4 | 8 | 12 |
---|---|---|---|
Time (minutes) | 5 | 10 | 15 |
Now consider the ratio table that shows the same information for Mark's printer.
Photos | 20 | 24 | 28 |
---|---|---|---|
Time (minutes) | 25 | 30 | 35 |
Kevin can knit six sweaters in 10 days.
We want to determine how many sweaters Kevin can knit in 15 days. We know that he can knit 6 sweaters in 10 days, so let's use this information to create a ratio table that relates the number of sweaters knit to the amount of time it takes to knit them.
Sweaters | 6 | ||
---|---|---|---|
Time | 10 |
We can scale the ratio of 6 sweaters in 10 days, 6:10, back by dividing both quantities by 2. This will tell us how many sweaters Kevin can knit in 5 days.
Sweaters | 6 | 6÷2=3 | |
---|---|---|---|
Time | 10 | 10÷2=5 |
We found an equivalent ratio of 3 sweaters knit in 5 days. We can use this ratio to find how many sweaters Kevin can knit in 15 days. Since 5* 3=15, we can scale the 3:5 ratio forward by 3 to find the missing information.
Sweaters | 6 | 6÷2=3 | 3* 3=9 |
---|---|---|---|
Time | 10 | 10÷2=5 | 5* 3=15 |
We found that Kevin can knit 9 sweaters in 15 days.
We want to determine how many days it takes Kevin to knit 12 sweaters, given that he can knit 6 sweaters in 10 days. Let's use this information to write the ratio of time spent knitting to the number of sweaters knit.
10days/6sweaters
We know that 6* 2=12. This means we can multiply both quantities in this ratio by 2 to get an equivalent ratio with a denominator of 12 sweaters.
10days* 2/6sweaters* 2=20days/12sweaters
We got 20 days in the numerator. This means that it took Kevin 20 days to knit 12 sweaters.
A vending machine at a school dispenses 70 snacks in 5 minutes.
We can create a ratio table to determine the number of snacks the vending machine would dispense in 7 minutes. We are given that the vending machine dispenses 70 snacks in 5 minutes. Let's add this information to the ratio table.
Snacks | 70 | ||
---|---|---|---|
Time | 5 |
Note that there is no integer we can multiply 5 by to get 7. Let's first find the unit rate of snacks to time by scaling the ratio 70:5 back. We can do this by dividing both quantities in the ratio by 5 and recording the result in the second column of the ratio table. Remember, a unit ratio must have a denominator of 1.
Snacks | 70 | 70÷5=14 | |
---|---|---|---|
Time | 5 | 5÷5=1 |
Next, we can scale the unit ratio forward to 7 minutes by multiplying it by 7. This will give us the number of snacks the vending machine would dispense in 7 minutes.
Number of Snacks | 70 | 14 | 14*7=98 |
---|---|---|---|
Time | 5 | 1 | 1*7=7 |
Therefore, the vending machine would dispense 98 snacks in 7 minutes.
Let's start by recalling that the vending machine dispenses 70 snacks in 5 minutes. We can represent this information as a ratio of time to snacks dispensed.
5minutes/70snacks
We can use this ratio to create a ratio table that will help us to determine how long it would take for the vending machine to dispense 420 snacks. Let's multiply the numerator and the denominator of the ratio by 1, 2, 3, and so on, up to 7, to get the corresponding time and snacks for each equivalent ratio.
Time | 5 | 10 | 15 | 20 | 25 | 30 | 35 |
---|---|---|---|---|---|---|---|
Snacks | 70 | 140 | 210 | 280 | 350 | 420 | 490 |
This means that it would take the machine 30 minutes to dispense 420 snacks. In this case, we were able to find the solution because 420 is a multiple of 70. Another number of snacks might require numbers beyond integers.
Dylan and Emily are putting together a charity fundraiser at their school. They have both been selling tickets for the event. Dylan has sold 3 out of every 5 tickets.
Dylan and Emily sold tickets for a charity fundraiser event. We know that Dylan sold 3 out of every 5 tickets sold. Let's represent this information as the ratio of tickets sold by Dylan to the total number of tickets sold. 3:5 We want to determine the total number of tickets sold if Dylan sold five more tickets than Emily. First, let's create a ratio table with ratios that are equivalent to 3:5.
Tickets Sold by Dylan | 3 | 6 | 9 | 12 | 15 | 18 |
---|---|---|---|---|---|---|
Total Tickets Sold | 5 | 10 | 15 | 20 | 25 | 30 |
We can find the number of tickets sold by Emily by calculating the difference between the total number of tickets sold and the number of tickets sold by Dylan.
Total Tickets Sold | Tickets Sold by Dylan | Difference | Tickets Sold by Emily |
---|---|---|---|
5 | 3 | 5-3 | 2 |
10 | 6 | 10-6 | 4 |
15 | 9 | 15-9 | 6 |
20 | 12 | 20-12 | 8 |
25 | 15 | 25-15 | 10 |
30 | 18 | 30-18 | 12 |
We now have the total number of tickets sold by both Dylan and Emily. Let's subtract the number of tickets sold by Emily from the number of tickets sold by Dylan to find the difference between the total tickets sold by Dylan and Emily.
Tickets Sold by Dylan | Tickets Sold by Emily | Difference | Extra Tickets Sold by Dylan |
---|---|---|---|
3 | 2 | 3-2 | 1 |
6 | 4 | 6-4 | 2 |
9 | 6 | 9-6 | 3 |
12 | 8 | 12-8 | 4 |
15 | 10 | 15-10 | 5 |
18 | 12 | 18-12 | 6 |
Now, we were told that that Dylan sold 5 tickets more than Emily. The only option in the table that meets this description is if 25 total tickets were sold.
A delivery truck travels 220 miles in 4 hours, while a delivery van travels 180 miles in 3 hours.
Let's write the rate of the distance each vehicle travels to the amount of time it spent traveling. We know that the delivery truck travels 220 miles in 4 hours and that the delivery van travels 180 miles in 3 hours. cc Delivery Truck & & Delivery Van 220mi:4h & & 180mi:3h Next, we can determine the unit rates for each vehicle. Remember, finding the unit rate means that we need to get 1 on the right-hand side of each rate. Let's divide the delivery truck's rate by 4 to find its unit rate.
This means that the delivery truck travels 55 miles in 1 hour. Now let's calculate the unit rate for the delivery van by dividing both quantities by 3.
The delivery van travels 60 miles in 1 hour. Since the delivery van has a higher unit rate, it is faster than the delivery truck.
Consider the unit rates found in Part A for each vehicle.
cc
Delivery Truck & & Delivery Van
55mi:1h & & 60mi:1h
We can create two equivalent rates by scaling up these rates by 5. That will show us the distance traveled by both vehicles after 5 hours.
cc
Delivery Truck& &Delivery Van
55mi* 5:1h* 5& &60mi* 5:1h* 5
⇓& &⇓
275mi:5h& &300mi:5h
The delivery truck will travel 275 miles after 5 hours, while the delivery van will travel 300 miles. Let's subtract the distance the truck can travel from the distance the van can travel to find out how much further the delivery van will go.
300-275=25miles