8
round each number to the nearest 10, then
640 ÷ 80 = 8 ← estimate
Answer:
(B). 32
Step-by-step explanation:
ounces when converted to a decimal number is (5+(1/4)=5+0.25 = 5.25 ounces.
Now if 168 cookies weight 5.25 ounces, there are

32 cookies in an ounce, which is choice B.
ANSWER
Options B, C and D have exactly 2 significant figures.
<u>EXPLANATION</u>
To see whether the numbers have exactly 2 significant figures, round all to 2 significant figures. The ones that remains the same have exactly 2 significant figures.
yards to 2.s.f
gallons to 2.s.f
feet to 2.s.f
litters to 2.s.f\
meters to 2.s.f