Problem Solving | OG 2021 700 Level

DAM1997 wrote: ↑

Sat Nov 28, 2020 12:03 am

A certain state's drinking water production was 980 million pounds in 2007 and 2.7 billion pounds in 2014. Approximately how many more million gallons of drinking water did the state produce in 2014 than in 2007 ? (1 billion = 10^9 and 1 gallon = 8.6 pounds.)

A. 100
B. 200
C. 1,700
D. 8,200
E. 14,800

IMPORTANT: Notice that the answer choices are very spread apart. This means we can probably use some ESTIMATION to find the answer quickly.

2007 milk production = 980,000,000 POUNDS
2014 milk production = 2,700,000,000 POUNDS

Sense of the question asks us to provide our answer in MILLIONS of gallons, let's rewrite are given information in terms of MILLIONS
2007 milk production = 980 MILLION POUNDS
2014 milk production = 2,700 MILLION POUNDS

Difference = 2,700 million pounds - 980 million pounds (too much work!)
Let's round up a little bit and say 2007 milk production ≈ 1,000 million pounds

Difference ≈ 2,700 million pounds - 1,000 million pounds ≈ 1,700 million pounds

Given: 1 gallon = 8.6 pounds

So, the number of GALLONS = (1,700 million pounds)/(8.6 pounds per gallon) ≈ 200 million gallons

Answer: B

Cheers,
Brent