Multiple choice

What is the ratio of the mean proportional between 1.6 and 3.6 and the third proportional of 5 and 8 ?

  1. 2:15

  2. 5:16

  3. 3:16

  4. 4:15

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

Mean proportional of a and b is √(ab) = √(1.6 × 3.6) = √5.76 = 2.4. Third proportional of 5 and 8 means if 5:8 = 8:x, then x = 64/5 = 12.8. Ratio = 2.4:12.8 = 24:128 = 3:16.