Question

A scientist measured the length of a laboratory rat. It was 6.42 inches. The next time she measured it, the rat had grown to a length of 7.323 inches.

How much did the length of the laboratory rat increase?

A. 0.903 inches

B. 1.103 inches

C. 6.681 inches

D. 13.743 inches

Answer 1

A) 0.903
You have to subtract 

Answer 2

So to answer this question you take the length of the rat right now minus the length that is was.  So you take 7.323 - 6.42 = 0.903.  And to double check your answer you can take 6.42 + 0.903 = 7.323.  Your answer is A. 0.903 inches the rat had grown.