P is 6 times greater than Q then by what per cent is Q smaller than P?

Answer: Option D

Let Q = 10.
Then, P = 60.
Q is 50 less than P.
Q, % less than P = $$\frac{50}{60}\times 100=83.33\%$$

Alternative Method
10 (Q) == (6 times greater) ==> 60(P) == x%↓(Less than Q) ==> 10 (Q)
Now,
$$\text{x}=\frac{50\times 100}{60}=83.33\%$$