A student bought 84 pencils. If he sharpened 35 pencils, what is the ratio of the unsharpened pencils to the sharpened pencils?

Number of pencils bough by the student = 84

Number of pencils sharpened by the student = 35

Then

The number of pencils that was not sharpened = (84 - 35)

= 49

So 35 pencils have been sharpened and 49 pencils have not been sharpened.

Then Number of pencils unsharpened:Number of pencils sharpened = 49:35

= 7:5

So the ratio of the number of unsharpened pencil to the number of sharpened pencil is 7:5