Question

Out of 1,100 discs tested, 13 are defective. Estimate the number of defective discs in a batch of 41,000.

Answer 1

13/1,100 = x/ 41,000 (in English, this reads 13 out of 1,100 equals x out of 41,000) * by 41,000 and you get 41,000 x 13/1,100 = x
which is about 485