Question

An air-conditioner manufacturer randomly samples 50 units and finds that 2 are defective. The company ships 1200 units each month.

Which is the best prediction for the number of defective units in the monthly shipment?

25

24

48

50

Answer 1

48

First, you have to set two fractions so that they're equal, we can set it up so that it's defective/total, so then we have 2/50=x/1200

Now, we cross multiply so that it's 2400=50x

Next, we divide both sides by 50, so that it's 2400/50 =x

One trick we can do is cross out the mutual 0's, so now it's 240/5, which is 48