Question

Brandon was getting his garden ready. Soil came in bags of 1.3 cubic feet. He needed 8 cubic feet of soil.

Which best explains a reasonable number of bags of soil to buy?

A.
1.3 cubic feet is about 1 cubic foot, so 8 bags will give him a bit less than 8 cubic feet of soil. He should get 8 bags of soil.

B.
2 bags will give him about 3 cubic feet. So 6 bags will give him a bit more than 8 cubic feet. He should get 6 bags of soil.

C.
For every 3 bags of soil, he gets a bit less than 4 cubic feet. So 6 bags will give him a bit less than 8 cubic feet. He should get 7 bags of soil.

Answer 1

Let's look at each answer separately:
A: we can't say that 1.3 cubic feet is about 1 cubic foot (there's a difference of 0.3 feet) and that 8 bags will give us a little less than 8 cubic feet - if we calculate 8*1.3 that'd give 10.4 cubic feet, which is much more than required

B: 2 bags will not give him a little less than 3 cubic feet (there's a difference of 0.6 feet) and so 6 bags will not give him a bit more than 8 cubic feet - if we calculate 1.3*6 we get 7.8 cubic feet, which is not enough

C: This answer is the most reasonable since the amount in 3 bags (3*1.3 = 3.9 cubic feet) is very close to 4 cubic feet, and so 6 bags would give him a little less than 8 cubic feet and thus he would require 7 bags