Which smallest positive number should be subtracted from each of 9 and 13 so that 18 is the third proportion to them?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is Option 4 i.e. 1.
Concept used:
If x is the third proportion of a and b then
⇒ x = b2/a
Calculations:
Let x be the smallest number.
⇒ (9 - x)/(13 - x) = (13 - x)/18
⇒ 162 - 18x = x2 + 169 - 26x
⇒ x2 - 8x + 7 = 0
We get, x = 1 and 7
Hence, the smallest positive number is 1.