A plumber needs to drill a hole that is just slightly larger than 3/16 of an inch in diameter. Which measurement is the smallest but still larger than 3/16?

5/16 inch. 13/64 inch. 9/32 inch.

All we need to do is to find a common denominator for each of the fractions. It's quite easy in this case because each denominator is an iteration of 16, so so LCD is 64:

5/16 = 20/64

13/64 stays the same

9/32 = 18/64

And the hole's size: 3/16 = 12/64

12/64 < 13/64 < 18/64 < 20/64

So the smallest measurment but still larger than 3/16 (12/64) is 13/64 inch.