7th Grade Math

326 Percent

Another method for estimating the percent of a number is first to find

10% of the number and then multiply. For example, 70% = 7 · 10%.

So, 70% equals 7 times 10% of the number.

MONEY Marita and four of her friends ordered a pizza that cost

$14.72. She is responsible for 20% of the bill. About how much

money will she need to pay?

Method 2 Use 10% of a number to estimate.

Step 1 Find 10% of $15.00.

10% of $15.00 = 0.1 · $15.00

= $1.50

Step 2 Multiply.

20% of $15.00 is 2 times 10% of $15.00.

2 · $1.50 = $3.00

To multiply by 10%, move the

decimal point one place to the left.

Method 1 Use a fraction to estimate.

20% is _ 102 or _^15.

20% of $14.72 ≈ _^15 · $15.00 20% = _^15 and round $14.72 to $15.00.

≈ $3.00 Multiply.

So, Marita should pay about $3.00.

b. MONEY Dante plans to put 80% of his paycheck into a savings

account. His paycheck this week was $295. About how much

money will he put into his savings account?

You can also estimate percents of numbers when the percent is greater

than 100 or less than 1.

Percents Greater Than 100 or

Less Than 1

Estimate 122% of 50.

122% is about 120%.

120% of 50 = (100% of 50) + (20% of 50) 120% = 100% + 20%

= ( 1 · 50 ) + (^) ( ^1
5
· (^50) ) 100% = 1 and 20% = ^15
= 50 + 10 or 60 Simplify.
So, 122% of 50 is about 60.
Check for Reasonableness
When estimating the
percent of a number and
the percent is greater than
100, the estimate will
always be greater than
the number.
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