Multiple choice

Jamie has 14 bottles, each of a different height, in inches. If he adds the heights of two more bottles having the same height, then their average height increases by 1 inch. What is the height of each bottle he added so that the average height after including them is 15 inches?

  1. 14 inches

  2. 20 inches

  3. 22 inches

  4. 32 inches

  5. 44 inches

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

Let S be the sum of the 14 original heights. The average is S/14. After adding two bottles of height x, the new sum is S + 2x and the new average is (S + 2x)/16 = 15, so S + 2x = 240. We are given that (S + 2x)/16 = S/14 + 1. Substituting S = 240 - 2x into this equation gives (240)/16 = (240 - 2x)/14 + 1, which simplifies to 15 = (120 - x)/7 + 1. Solving for x gives 14 = (120 - x)/7, so 98 = 120 - x, resulting in x = 22.