Solved Examples and Worksheet for Estimation-Decimals

Q1Each flower bouquet costs $1.85 in a flower shop. How many bouquets will you get for$16 by estimating the cost of the bouquet to the nearest whole number?

A. 8
B. 7
C. 11
D. 9

Step: 1
The cost of each flower bouquet is $1.85. Step: 2 Rounding to the nearest whole number, the cost is$2. [The digit in the tenths place is 8, which is greater than 5. So, add 1 to the digit in the units place and delete all the decimal places.]
Step: 3
The number of bouquets we get for $16 = 162 = 8. Correct Answer is : 8 Q2Estimate the product of 11.62 and 5.46. Round to the nearest whole number. A. 60 B. 55 C. 50 D. 66 Step: 1 11.62 × 5.46 [Original factors.] Step: 2 11.62 when rounded to nearest whole number becomes 12. [The digit in the tenths place is 6, which is greater than 5. So, round up the whole number.] Step: 3 5.46 when rounded to the nearest whole number becomes 5. [The digit in the tenths place is 4, which is less than 5. So, round down the whole number.] Step: 4 12 × 5 [Replace the original factors with their rounded values.] Step: 5 = 60 [Multiply.] Step: 6 So, the estimated product of 11.62 and 5.46 = 60. Correct Answer is : 60 Q3Estimate the quotient of 36.10 ÷ 17.77. Round to the nearest whole number. A. 3 B. 4 C. 2 D. 5 Step: 1 36.10 ÷ 17.77 [Original numerical expression.] Step: 2 = 36 ÷ 18 [Round 36.10 to the nearest whole number 36 and 17.77 to the nearest whole number 18.] Step: 3 = 2 [Divide.] Correct Answer is : 2 Q4Between which two numbers does the quotient of 18.93 ÷ 3 lie? A. 4 and 5 B. 6 and 7 C. 7 and 8 D. 5 and 6 Step: 1 18.93 ÷ 3 [Original numerical expression.] Step: 2 = 18 ÷ 3 [Use compatible number such as 18 for 18.93.] Step: 3 = 6 [Divide.] Step: 4 As 18.93 is greater than 18, the quotient of 18.93 ÷ 3 will also be greater than 6. Step: 5 So, the quotient of 18.93 ÷ 3 lies between the numbers 6 and 7. Correct Answer is : 6 and 7 Q5Estimate the product of 0.97 and 78.76 by rounding each factor to the nearest whole number. A. 79 B. 78 C. 80 D. 81 Step: 1 0.97 × 78.76 [Original factors.] Step: 2 1 × 79 [Rounding 0.97 to the nearest whole number 1 and 78.76 to the nearest whole number 79.] Step: 3 79 [Multiply.] Step: 4 The estimated product of 0.97 and 78.76 after rounding each factor to the nearest whole number is 79. Correct Answer is : 79 Q6Estimate the product of 78.9 and 43.3 using compatible numbers. A. 3180 B. 3220 C. 3210 D. 3200 Step: 1 Compatible numbers are numbers that are easy to compute mentally. Step: 2 78.9 × 43.3 [Original factors.] Step: 3 = 80 × 40 [Use compatible numbers such as 80 for 78.9 and 40 for 43.3.] Step: 4 = 3200 [Multiply.] Step: 5 The estimated product of 78.9 and 43.3 using compatible numbers = 3200. Correct Answer is : 3200 Q7Lydia earns$3.68 per hour for baby sitting in a daycare. Estimate her earnings in 2.7 hours by rounding each factor to the nearest whole number.
A. $9 B.$12
C. $17 D.$14

Step: 1
3.68 × 2.7
[Original factors.]
Step: 2
= 4 × 3
[Rounding 3.68 to the nearest whole number 4 and 2.7 to the nearest whole number 3.]
Step: 3
= 12
[Multiply.]
Step: 4
Lydia earns about $12 in 2.7 hours. Correct Answer is :$12
Q8The average rainfall in two different cities are 19.13 in. and 29.76 in. Which of the following is the best estimate of the difference between the two rainfalls?

A. 11 in.
B. 30 in.
C. 1.1 in.
D. 20 in.

Step: 1
The average rainfall in two different cities are 19.13 in and 29.76 in .
Step: 2
The average rainfall of one city = 19.13 = 19
(19.13 Rounded down to 19)
Step: 3
The average rainfall of another city = 29.76 = 30
(29.76 Rounded up to 30)
Step: 4
The difference between the two rainfalls = 30 - 19 = 11
Step: 5
So, the difference between the two rainfalls is 11 in.
Correct Answer is :   11 in.
Q9Estimate the sum of 2.215 and 4.617 by rounding the decimals to the nearest whole numbers.

A. 7
B. 9
C. 6
D. 8

Step: 1
2.215 + 4.617
[Original expression.]
Step: 2
The digit in the tenths place of 2.215 is 2, which is less than 5.
Step: 3
So, round the decimal 2.215 to the nearest whole number 2.
Step: 4
The digit in the tenths place of 4.617 is 6, which is greater than 5.
Step: 5
So, round the decimal 4.617 to the nearest whole number 5.
Step: 6
= 2 + 5
[Replace the decimals with their rounded values in the original expression.]
Step: 7
= 7
[Add.]
Step: 8
The estimated sum of the two decimals after rounding to the nearest whole numbers = 7.
Correct Answer is :   7
Q10Roy bought a toy car for $1.64 and his sister bought a Barbie doll for$5.42. Estimate the money they spent.
A. $4 B.$5
C. $7 D.$10

Step: 1
If the digit in the tenths place is greater than or equal to 5, round the decimal up. Otherwise, round the decimal down.
Step: 2
The decimals 1.64 and 5.42 are rounded to whole numbers 2 and 5.
[1.64 is rounded up and 5.42 is rounded down.]
Step: 3
Estimated money spent = $2 +$5 = $7. Correct Answer is :$7
Q11Estimate the value of 31.98 ÷ 4.316.

A. 8
B. 11
C. 18
D. None of the above

Step: 1
Estimated result of the question can be obtained by dividing the two numbers after converting them to the whole numbers.
Step: 2
The rounded to the whole number of 31.98 is 32 and of 4.316 is 4.
Step: 3
The result 324 = 8.
Correct Answer is :   8
Q12Which of the following numbers indicates the estimated product of 1.917 and 17.949?

A. 36
B. 88
C. 48
D. None of the above

Step: 1
1.917 2
[Round to the whole number.]
Step: 2
17.949 18
[Round to the whole number.]
Step: 3
The product of two numbers = 2 × 18 = 36.
Correct Answer is :   36
Q13The temperature of a city in the morning was 8.6°C and in the afternoon it was 12.1°C. About how many degrees had the temperature gone up?
A. 3°C
B. 20°C
C. 2°C
D. 10°C

Q14Tanya earns $2.81 per hour for baby sitting in a daycare. Estimate her earnings in 2.6 hours by rounding the values to their nearest whole numbers. A.$9
B. $14 C.$11
D. $6 Step: 1 Money earned by Tanya in 2.6 hours = 2.81 × 2.6 [Original factors.] Step: 2 = 3 × 3 [Rounding 2.81 to the nearest whole number 3 and 2.6 to the nearest whole number 3.] Step: 3 = 9 [Multiply.] Step: 4 Tanya earns about$9 in 2.6 hours.
Correct Answer is :   $9 Q15Wilma went to 8 stores to buy tapes. She spent$54.84 shopping at each store. Estimate how much Wilma spent altogether by rounding the factors to the nearest whole numbers.
A. $448 B.$432
C. $440 D.$445

Step: 1
Let m be the money Wilma spends at each of the 8 stores she visits.
Step: 2
Wilma spends $54.84 in buying tapes at each of the 8 stores she visits. Step: 3 m = 8 x 54.84 [Original factors.] Step: 4 m = 8 x 55 [Round 54.84 to the nearest whole number 55.] Step: 5 m = 440 [Multiply.] Step: 6 Wilma spent$440 altogether for buying tapes at each store.
Correct Answer is :   \$440