Question

chapter 2 → lesson 8: add, subtract, multiply, & divide decimals

1. at a math competition, three members of a team each solved a problem as quickly as they could. their times were 4.18 seconds, 3.75 seconds, and 3.99 seconds. what was the total of their times?

a 11.92 seconds
b 10.99 seconds
c 10.72 seconds
d 11.72 seconds

1. beginning with the number 6.472, add:

1 hundredth
3 ones
5 tenths
what is the result?
a 7.822
b 6.823
c 9.982
d 6.607

1. find the perimeter (total length of all four sides) of a trapezoid whose sides measure 2.09 ft, 2.09 ft, 3.72 ft, and 6.60 ft.

a 16.12 ft
b 14.5 ft
c 13.50 ft
d 8.56 ft

1. find the difference:

$85.37 - 75.2 =$
a 160.57
b 10
c 10.35
d 10.17

1. subtract:

$3.64 - 1.46 =$
a 2.18
b 4.18
c 1.18
d 4.20

Explanation:

Step1: Sum the three times

$4.18 + 3.75 + 3.99 = 11.92$

Step2: Convert values to decimals

1 hundredth = $0.01$, 3 ones = $3$, 5 tenths = $0.5$

Step3: Add to initial number

$6.472 + 0.01 + 3 + 0.5 = 9.982$

Step4: Sum all trapezoid sides

$2.09 + 2.09 + 3.72 + 6.60 = 14.50$

Step5: Align decimals and subtract

$85.37 - 75.20 = 10.17$

Step6: Align decimals and subtract

$3.64 - 1.46 = 2.18$

Answer:

1. A. 11.92 seconds
2. C. 9.982
3. B. 14.5 ft
4. D. 10.17
5. A. 2.18