Question

A man travels the first part of his journey at 20 km/h and the next at 70 km/h, covering the entire journey at an average speed of 50 km/h. What is the ratio of the distace that he covered at 20 km/h to that he covered at 70 km/h?

• A. 4:21
• B. 3:22
• C. 1:4
• D. 3:5

Answer 1

The correct option is A 4:21

By alligation rule

Ratio ot time = 2:3
$\therefore$ Ratio of distances = 2 $\times$ 20 : 3 $\times$ 70 = 4 : 21

Alternatively:
$\frac{x}{20}+\frac{y}{70}=\frac{x+y}{50}$
$\Rightarrow \frac{76x+20y}{1400}=\frac{x+y}{50}$
$\Rightarrow 42x=8y\Rightarrow \frac{x}{y}=\frac{4}{21}$