To find the % of a given number use the following steps :

1) Obtain the number, say x.

2) Let the percent as p%.

3) P% of x

4) write these as a proportion as p/100 = ?/x

5) Now cross multiply and find the value of "?" mark.

1) 30 % of 180

30/100 = x/180

Cross multiply

100x = 30 . 180

100x = 5400

∴ x = 5400/100

= 54

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2) 75 % of 400

75/100 = x/400

Cross multiply

100x = 75 . 400

100x = 30,000

X = 30,000/100

x = 300

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3) 3 ⅓ of 90 km

3 ⅓/100 = x/90

(10/3)/100 = x/90 [ convert mixed fraction to improper]

10/300 = x/90

Cross multiply

300x = 10 . 90

300x = 900

x = 900/300

x = 3 km

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4) 2.5 % of 800 meters

2.5/100 = x/800

Cross multiply

100x = (2.5) . 800

100x = 2,000

x = 2,000/100

x = 2 meters

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1) 5% of $1400

5 % of 1400

As there is a % sign with 5 so write 5% as 5/100, "of" means multiplication so multiply by 1400.

(5/100) x 1400

(5 x 1400)/100

7,000 /100

=$70

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2) 16 % of 25 liters.

16 % of 25

As there is a % sign with 16 so write 16% as 16/100, "of" means multiplication so multiply by 25.

(16/100) x 25

(16 x 25)/100

400 /100

= 4 liters

• Conversion of Percentage to Fraction

• Conversion of Fraction to Percent

• Conversion of Percentage to Decimal

• Conversion of Decimal to Percent

• Find the Percentage of a given number

• What Percent is one number of another number

• Percentage as a comparison of two quantities

• Increase Percent

• Decrease Percent

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