Estimating with Percents

Chapter 5.4 B

Percent-Fractions you should memorize!

20% = 1/5 50% = 1/2 80% = 4/5 25% - 1/4 33% = 1/3

30% = 3/10 60% = 3/5 90% = 9/10 75% = 3/4 66% = 2/3

40% = 2/5 70% = 7/10 100% = 1

Percent-Fractions you should memorize!

10% = 1/10 20% = 1/5 25% = 1/4 30% = 3/10 33% = 1/3

40% = 2/5 50% = 1/2 60% = 3/5 66% = 2/3 70% = 7/10

75% = 3/4 80% = 4/5 90% = 9/10 100% = 1

How can you find 20% of 58?Since we know 20% is also 1/5, we need to

come up with a number that is close to 58 and divides by 5.15

of 60

60 ÷ 5 = 12So 20% of 58

is ABOUT 12

How can you find 76% of 22?This time we need to change 76% to 75%

because the fraction 3/4 is easier. THEN change 22 to something that divides by 4!

34

of 20

20 ÷ 4 = 5Since the top number is 3 we have to multiply by that (it’s like

mentally finding 3/5!!!

So 5 x 3 = 15, which means 76% of 22 is ABOUT

15

We use this in the real world ALLLLLLLLLLLLLLLL the time!!!

78% of the Mako team scored a level 3 or higher on the FCAT. There are 181 kids on the team. ABOUT how many kids scored 3 or higher?

45

of 180

180 ÷ 5 = 36Since the top number is 4 we have to multiply by that!

So 36 x 4 = 144, which means 78% of 181 is ABOUT

144 students

Find 55% of 42Some percents are in between 2 others (like

55%) so you may have to do 2 problems!

12

of 40

40 ÷ 2 = 20

Since 55 is between these 2 find the number that is also between

the 2 answers!

35 of 40

40 ÷ 5 = 88 x 3 = 24