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| 9 Theory slides |
| 11 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.
Take a look at a container with a total capacity of 60 liters. Move the slider to fill it with a liquid. See how the number of liters of the liquid relates to the percent of the occupied container.
ofis often used to indicate a product in math expressions. This means that 52 of 86 is the same as the product of 52 and 86.
ca⋅b=ca⋅b
ba=b/50a/50
Multiply
1a=a
ofindicates multiplication.
ca⋅b=ca⋅b
ba=b/25a/25
Multiply
1a=a
ofindicates multiplication.
a%=100a
ba=b/20a/20
Calculate quotient
ca⋅b=ca⋅b
ba=b/5a/5
Multiply
1a=a
a%=100a
ba=b/20a/20
Calculate quotient
ofoften indicates multiplication.
a%=100a
ba=b/20a/20
Calculate quotient
ca⋅b=ca⋅b
ba=b/5a/5
Multiply
1a=a
ca⋅b=ca⋅b
ba=b/2a/2
Multiply
Calculate quotient
a%=100a
ba=b/2a/2
ca⋅b=ca⋅b
Cross out common factors
Simplify quotient
1a=a
Number | Percent | Fraction |
---|---|---|
10 | 10% | 101 |
20 | 20% | 51 |
25 | 25% | 41 |
50 | 50% | 21 |
75 | 75% | 43 |
Find the percent of each number.
To find 34 % of 68, we will first write the percent as a decimal. Divide 34 % by 100 % by moving the decimal point two places to the left. 34 %/100 %= 0.34 Now, we can calculate 34 % of 68 by multiplying the equivalent decimal number 0.34 by 68. 34 % of 68 &= 0.34 * 68 &⇓ 34 % of 68 &= 23.12 We get that 34 % of 68 is 23.12.
This time we need to calculate 0.75 % of 220. Note that 0.75 % is a very small percent, less than 1 %. First, divide it by 100 % to rewrite the percent as a decimal. 0.75 %/100 %=0.0075 Next, calculate the product of this decimal number and 220. 0.75 % of 220 &= 0.0075 * 220 &⇓ 0.75 % of 220 &= 1.65
We need to calculate 180 % of 5. Let's begin by rewriting the percent as a fraction. We will use the definition of a percent. n %=n/100 Substitute n with 180 and then simplify the fraction as much as possible.
Next, we can calculate 180 % of 5 by multiplying the equivalent fraction 95 by 5. 180 % of 5=9/5* 5 To calculate this product, multiply the numerator 9 by 5 and write the same denominator. Also, note that we can then reduce the fraction by 5 instead of multiplying.
Therefore, 180 % of 5 is 9.
It can be difficult to calculate 36 % of 75. Let's use the fact that we can switch the numbers and the result will still be the same. 36 % of 75 ⇕ 75 % of 36 The percent 75 % is equivalent to the fraction 34.
This means that we can calculate 75 % of 36 by multiplying 34 by 36.
It can be concluded that 75 % of 36 is 27, just as 36 % of 75 is 27.
We need to calculate 167 % of 200. This is equivalent to calculating 200 % of 167. 167 % of 200 ⇕ 200 % of 167 Rewrite the percent as a decimal number by dividing it by 100 %. 200 %/100 %=2 Next, multiply 2 by 167 to calculate 200 % of 167. 2* 167 =334 Our calculations show that 200 % of 167 is 334, just as 167 % of 200 is 334.
Let's start by interchanging the percent and the number. 66 % of 50 ⇕ 50 % of 66 The fraction equivalent of 50 % is 12. Next, multiply the fraction by 66 to evaluate the percent. 1/2* 66=66/2=33 Our calculations show that 66 % of 50 is 33.
Estimate each percent.
We want to estimate 52 % of 81. We will start by rounding each number. c|c 52is closer to50 & 81is closer to80 than to60 & than to90 ⇓ & ⇓ 52 % ≈ 50 % & 81≈ 80 Now we multiply the rounded numbers to get an estimation. Note that we can write 50 % as the fraction 12.
We found that 52 % of 81 is about 40.
This time we want to estimate 35 % of 69. Since 35 is a quite convenient number, we will only round the second number 69. 69is closer to70 [-0.1cm] than to60 [-0.1cm] ⇓ [-0.1cm] 69 % ≈ 70 % Next, multiply 35 % by 70 to get an estimation. Start by rewriting the percent as a fraction with the numerator 35 and denominator 100.
We found that 35 % of 69 is about 24.5.
We want to estimate 19 % of 244. Let's begin by rounding each number to a number that ends with 0. c|c 19is closer to20 & 244is closer to240 than to10 & than to250 ⇓ & ⇓ 19 % ≈ 20 % & 244≈ 240 Next, we can use the rounded number to find an estimation. Calculating 20 % of 240 requires rewriting the percent as a fraction and then multiply by 240.
We found that 19 % of 244 is about 48.
The number 244 can also be rounded to 245. This number does not end with 0 but it is convenient enough to simplify the following calculations. 244≈ 245 Let's calculate 20 % of 245.
Our works shows that 19 % of 244 is about 49. Previously, we estimated the percent to be about 48, which is a different number. 20 % of 240 &= 48 20 % of 245 & = 49 This is perfectly fine. Keep in mind that rounding numbers differently can result in different estimates. The important thing is that they both are close enough to the actual value of the percent, which is 46.36. 46.36 ≈ 48 ✓ 46.36 ≈ 49 ✓ Both 48 and 49 can be accepted as correct estimates of 19 % of 244.
Penguins spend about 75% of their lives in the sea. The life span of Emperor Penguins is 15 to 20 years.
We want to estimate 75 % of 19 years. Let's start by rounding the number of years. c 19is closer to20 than to10 ⇓ 19≈ 20 Now we can multiply the numbers to get an estimation. 75 % of 20 = 75 % * 20 First, rewrite the percent as a fraction by using the definition of a percent. In addition to that, let's simplify the fraction to work with smaller and more convenient numbers.
We found that 75 % of 19 years is about 15 years. This means that a penguin that lives 19 years spends about 15 years underwater.
Miguel is deciding wheter to buy a dress that originally cost $39.99 but is now on sale for 30% off.
About how much is the discount in dollars?We want to estimate 30 % of $39.99. We will start by rounding the cost of the dress. $39.99 ≈ $40 Now we multiply the percent by the rounded cost to get an estimation. First, we write the percent as a fraction with the numerator 30 and the denominator 100.
We found that 30 % of $39.99 is about $12. This means that dress has a discount of $12 and Miguel decides to buy it!