In a race of 200 m, B can give a start of 10 m to A and C can give a start of 20 m to B. The start that C can give to A in the same race is ?

Answer: Option B

B : A = 200 : 190
C : B = 200 : 180
$$\begin{array}{rl}& =\frac{C}{A}\\ & =\frac{C}{B}\times \frac{B}{A}\\ & =\frac{200}{180}\times \frac{200}{190}\\ & =\frac{200}{171}\end{array}$$
∴ C can give to A, a start of (200 - 171) m = 29 m