Max has a collection of stamps in three colors: 20 red stamps, 80 blue stamps and 7 yellow ones. He is trying to sell the whole collection. He already sold 20 red stamps for the price of $1.1 for each stamp and 80 blue stamps for the price of $0.8 for each stamp. What price did he need to set for each yellow stamp to be able to earn the total of $100 from the whole sale?
Thoughts? Step-by-step reasoning:
Max earned 20 * 1.1 = $22 on red stamps. From the blue stamps Max got 80 * 0.8 = $64. His earnings so far are 22 + 64 = $86. To earn $100 he needs 100 – 86 = $14 more. Max has 7 yellow stamps, so he needs to set the price at 14 / 7 = $2.
Thus, the answer is 2.