In a 100 m race, A can give B 10 m and C 28 m. In the same race B can give C:

Answer: Option B

$$\begin{array}{rl}& A:B=100:90\\ & A:C=100:72\\ & B:C=\frac{B}{A}\times \frac{A}{C}=\frac{90}{100}\times \frac{100}{72}=\frac{90}{72}\end{array}$$
When B runs 90 m, C runs 72 m.
When B runs 100m, C run
$$\left(\frac{72}{90}\times 100\right)m=80m$$
∴ B can give C 20 m