Question

In a bag, there are a total of 50 dimes and quarters. 40% of the coins are quarters and 35% of the quarters are on heads. How many of the quarters are on tails? ​

Answer 1

13 quarters must be tails.

Explanation:

Number of quarters = 40% of 50 coins

Number of quarters = 40/100 * 50 = 20 coins which are quarters.

35% of these 20 quarters on heads. We can proceed in 2 ways from here.

We can actually find the number of quarters that are on heads.

35/100 * 20 = 7 quarters are showing heads.

Since the other quarters must be tails 20 - 7 = 13 quarters must be tails.

The other way to do it is to realize that if 35% of the coins are heads, 65% of the coins must be tails 20 * 65/100 = 13 which is a bit more direct.