If 10 spiders can catch 10 flies in 10 min, then how many flies can 200 spiders catch in 200 min?

Correct Answer: 4000

Let the required number of files be

More spiders, More flies (Direct proportion)

More time, More flies (Direct Proportion)

(Spiders 10 : 200 )

(Time 10 : 200 ) :: 10 : x

Therefore, (10×10×x)=(200×200×10)

Hence,

 x = 200×200×1010×10 = 4000 files