Bunuel wrote:

When frightened, a certain puffer fish rapidly expands by 70%. Shortly thereafter, the fish contracts by 70%. By what approximate percentage does the puffer fish then need to expand again in order to return to its initial size?

A. 0%

B. 20%

C. 50%

D. 70%

E. 100%

let x be the original size

x expands by 70% => 1.7*x then contracts by 70% => 1.7*0.3*x = 0.51*x

To expand again in order to return to its initial size the puffer needs almost 50% to get back to original size x

So it needs to expand by 100%.

Hence Option E is correct.

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