In a store, a sample of 60 pens was selected from a box of 1,200 pens. of these 60, 4 pens did not work. about how many pens could be expected to not work in the group of 1,200 pens?

Ok so if 1200 total pens and 60 were taken that's a ratio of 1200/60=20

out of 60pens 4 didn't work, again ratio is 4/60=1/15 so about 1/15 of the pens didn't work. 

so we have 1200pens * 1/15broken ratio = 80 pens or we can say 

20*4=80pens won't work from 20 groups of 60 and 4 out of 60 not working is 20*4=80 not working from total batch of 1200.

hope this helps you some! thank you