Multiple choice

A postal clerk sold 75 stamps for a total of $10.85. Some of the stamps were 15-cent stamps and the remaining stamps were 13-cent stamps. How many of the stamps were 13-cent stamps?

  1. 15

  2. 20

  3. 25

  4. 30

  5. 35

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

If the numbers of 15 cents and 13 cents stamps were x and y respectively, we get the equation x + y = 75, and 15x + 13y = 1085. Multiplying the first equation by 15, we get 15x + 15y = 125. Subtracting the second equation from this, we get 2y = 40, or y = 20.

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