Three unequal resistors in parallel are equivalent to a resistance `1Omega`. If two of them are in the ratio `1:2` and if no resistance value is fractional, then the largest of the three resistances in ohms is

Options

A. 4
B. 6
C. 8
D. 12

Answer

B

Explanation

Two resistance are in ratio `1:2` and third resistance is R.
So, `1/x +1/(2x) + 1/R = 1 rArr x = 3/2(R/(R-1))`
As resistance is not fractional `rArr R/(R-1) = 2`
`rArr x = 3, R =2, 2x = 6`