Estimating With Percents

There are 4 girls in a class of 16 students.  What percent of the class is boys? 

• 12%

• 75%

• 50%

• 90%

Choose the best estimate for 66% of $357.99.

• $120

• $240

• $360

Calculate 25% of 80

• 20

• 80

• 48

• 95

• Neither because 2300 should have been used instead of 2400

• Maria is right because finding 10% of 2,400 and multiplying the result three is not a good way to approximate 27% of 2,365

Giselle estimated 165% of 81 by performing these steps. What did she do wrong?

(81)(170%)

=(81)(100% + 70%)

=(81)(100%) + (81)(70%)

=(81)(1.0) + (81)(0.70)

=(81) +(81.70)

• She rounded 165% to 170%

• She incorrectly multiplied 81 and 0.70

• She incorrectly broke up 190% into 100% + 90%

• She rounded 81 to 80

The Romero family dined at Las Burritos and their bill came to $34. They want to leave a 19% tip. This means they will pay 119% of the bill.

Which calculations results in the BEST estimate of the total amount they will pay in dollars? Assume there are no taxes.

• (30)(115%)

  =30(100% + 15%)

  =(30)(100%) + (30)(15%)

  =30 + (30)(10%) + 30(5%)

  =30 +3.0 + 2.0

  =35

• (30)(115%)

  =30(100% + 15%)

  =(30)(100%) + (30)(15%)

  =30 + (30)(10%) + 30(5%)

  =30 +3.0 + 1.5

  =34.5

• (30)(120%)

  =30(100% + 20%)

  =(30)(100%) + (30)(20%)

  =30 + (30)(10%) + 30(10%)

  =30 +3.0 + 3.0

  =36

• (30)(120%)

  =30(100% + 20%)

  =(30)(100%) + (30)(20%)

  =30 + (30)(10%) + 30(10%)

  =30 +3.0 + 3.0

  =39

Which is the BEST estimate of 25% of 239

• 58

• 60

• 50

• 62

Mrs. Phipps estimated 28% of 57 by rounding 28% to 30% and rounding 56 down to 50. She then multiplied 50 by 0.1 and got 5.0 and then multiplied that by 3 to get 15. Is her estimate reasonable?

• Yes because she correctly rounded 28% to 30

• Yes because she correctly rounded 56 to 50

• No because she incorrectly round 28% to 30

• No because she incorrectly rounded 56 to 50

What is 10% of 53?

What is 20% of 53?