Solved Examples and Worksheet for Application of Estimating Whole Numbers

Q1A music store has 58 shelves of CDs. Each shelf holds 42 CDs. Estimate the total number of CDs in the store.
A. 3,000
B. 2,400
C. 1,000
D. 100

Step: 1
Number of shelves in a music store = 58.
Step: 2
Number of CDs in each shelf = 42.
Step: 3
Round up 58 to 60 and round down 42 to 40.
Step: 4
Total number of CDs in the music store = number of shelves × number of CDs in each shelf
Step: 5
= 60 × 40 = 2400
[Substitute the values and simplify.]
Step: 6
Therefore, total estimated number of CDs in the store is 2,400.
Q2Sean collects postcards. He bought 768 postcards, of which 342 postcards were bought from Hungary and Sweden. The rest were bought from Canada. Rounding to the nearest ten, estimate the number of postcards that Sean bought from Canada.

A. 400
B. 230
C. 330
D. 430

Step: 1
Number of postcards that Sean bought from Canada = Total number of postcards - Number of postcards from Sweden and Hungary
Step: 2
= 768 - 342
Step: 3
= 770 - 340 = 430
[Round 768 and 342 to the nearest 10 and subtract the rounded values.]
Step: 4
The number of postcards bought from Canada rounded to the nearest ten, is 430.
Q3Shiela takes 12 minutes to decorate a vase. Estimate the time taken to decorate a vase 9 times
A. 98
B. 100
C. 102
D. 20

Step: 1
Round 12 down to 10 and 9 up to 10.
[Round to nearest multiple of 10.]
Step: 2
Time taken = 10 × 10 = 100
[Multiply.]
Step: 3
So, estimated time taken to decorate a vase 9 times is 100 minutes.
Q4Robert takes 19 minutes to prepare a flower bed. Estimate the time taken by him to prepare 9 flower beds.

A. 202 minutes
B. 298 minutes
C. 200 minutes
D. 30 minutes

Step: 1
Round 19 to 20 and 9 to 10.
[Round to nearest multiple of 10.]
Step: 2
Time taken by Robert to prepare 9 flower beds is about "20 × 10 = 200" minutes.
Correct Answer is :   200 minutes
Q5In a school there are 12 classes. Each class has about 47 students. Estimate the total number of students in the school.
A. 564
B. 400
C. 600
D. 500

Step: 1
Round 12 to 10 and 47 to 50.
[Round to nearest multiple of 10.]
Step: 2
Total number of students in the school = 10 × 50 = 500.
Q6Frank traveled 576 and 326 miles on two consecutive days. Estimate the total miles he traveled.
A. 800
B. 825
C. 890
D. 910

Step: 1
Frank traveled 576 and 326 miles on two consecutive days.
Step: 2
576 + 326 is about 580 + 330.
[Rounded to nearest 10]
Step: 3
= 580 + 330

Step: 4
= 910
Step: 5
Frank traveled a total distance of 910 miles on the two days together.
Q7543 people visited a museum on a particular Sunday. If the average cost of a ticket was $29, then about how much money did the museum collect on that day? A.$13,600
B. $16,200 C.$14,600
D. $12,400 Step: 1 Amount the museum collected on that day = Average price of the ticket × Number of people who visited the museum. Step: 2 =$29 × 543.
Step: 3
$29 can be rounded to$30.
Step: 4
543 can be rounded to 540.
Step: 5
So, $30 × 540 =$16,200.
Step: 6
So, $16,200 is the correct answer. Correct Answer is :$16,200
Q8A class of 59 students was divided into different groups containing 5 students in each of them. Estimate the number of groups that can be formed.

A. 10
B. 12
C. 11
D. 20

Step: 1
An estimate is enough to find the number of groups that can be made with 59 students.
Step: 2
Number of students in each group = 5
Step: 3
Total number of students in the class = 59
Step: 4
59 can be rounded to 60.
[Round 59 to nearest ten.]
Step: 5
Number of groups that can be made with the given number of students = Total number of students rounded to nearest ten ÷ Number of students in each group
Step: 6
= 60 ÷ 5 = 12
[Divide 60 by 5.]
Step: 7
Therefore, the estimated number of groups that can be formed is 12.
Q9Wilson bought 17 packs of pencils. There were 12 pencils in each pack. About how many pencils did he buy?
A. 350
B. 200
C. 250
D. 300

Step: 1
Round 17 up to 20 and 12 down to 10.
[Round to nearest multiple of 10.]
Step: 2
Number of pencils = 20 × 10
[Multiply.]
Step: 3
So, Wilson bought about 200 pencils.
Q10289 elementary school students and 120 middle school students wrote letters for a time capsule. Estimate the total number of letters written.
A. 500
B. 300
C. 400
D. 440

Step: 1
Round up 289 to the nearest hundred = 300
Step: 2
Round down 120 to the nearest hundred = 100
Step: 3
300 + 100 = 400
Step: 4
So, the estimated number of letters written are about 400.
Q11Amy has collected 831 marbles. If she wants to collect 1,000 marbles, estimate how many more marbles she needs to collect.
A. 100
B. 200
C. 300
D. 70

Step: 1
Amy has collected 831 marbles.
Step: 2
Round down 831 to 800.
[Rounded to the nearest 100.]
Step: 3
She wants to collect 1,000 marbles.
Step: 4
So, the number of marbles she needs to collect = 1,000 - 800 = 200.
Q12John wants to pack 5 oranges in each box. He has 38 oranges. Estimate the number of boxes he needs to place all the oranges.
A. 9
B. 8
C. 11
D. 10

Step: 1
John wants to pack 5 oranges in each box and he has 38 oranges.
[Given.]
Step: 2
38 can be rounded to 40.
Step: 3
Number of boxes required = Estimated number of oranges ÷ Number of oranges in each box.
Step: 4
= 40 ÷ 5 = 8
Step: 5
Therefore, John needs about 8 boxes to pack all the oranges.
Q13Ursula wants to use 4 roses in each bouquet. She has 77 roses. Estimate the number of bouquets she can make by using all the roses.
A. 20
B. 10
C. 15
D. 9

Step: 1
Ursula wants to use 4 roses in each bouquet and she has 77 roses.
[Given.]
Step: 2
77 can be rounded to 80.
Step: 3
Number of bouquets = Estimated number of roses ÷ Number of roses in each bouquet.
Step: 4
= 80 ÷ 4 = 20
Step: 5
Therefore, Ursula can make about 20 bouquets by using 77 roses.
Q14Paula played a game with Rachel in which the person who wins the round will earn 33 points. Paula won 6 out of 9 rounds. Estimate the points Paula had at the end of the game.

A. 240
B. 180
C. 160
D. 220

Step: 1
Number of points for each round = 33
Step: 2
33 points can be rounded as 30 points.
[Round to the nearest tens.]
Step: 3
Number of rounds played = 9
Step: 4
Number of rounds won by Paula = 6
Step: 5
Points earned by Paula at the end of the game = Number of points earned by Paula in each round × Number of rounds she won
Step: 6
= 30 × 6
Step: 7
= 180
Step: 8
Therefore, Paula earned 180 points in the game.
Q15Cost of an item is $29. Estimate the cost of 48 such items. A.$4,000
B. $80 C.$1,500
D. $800 Step: 1 Cost of an item =$29
= $1500 Correct Answer is :$1,500