Question

A person takes 40 minutes more than his usual time when he covers a distance of 20 km at 5 km/h. If he covers the same distance at 10 km/h, he takes x minutes less than the usual time. What is the value of x ?

1. 120
2. 80
3. 100
4. 60

Answer 1

Correct Answer - Option 2 : 80

Given:

A person takes 40 minutes more than his usual time when he covers a distance of 20 km at 5 km/h. If he covers the same distance at 10 km/h, he takes x minutes less than the usual time. 

Concept used:

Time and distance

Calculation:

Time = \(\frac{{{\rm{Distance}}}}{{{\rm{Speed}}}}\)

T₁ = \(\frac{{20}}{5} = 4km/hr\)

T₂ = \(\frac{{20}}{{10}} = 2km/hr\)

T₁ : T₂ = 2 : 1

Usual time = T₁ and new time = T₂

As per the question,

Difference of time = 40 unit

⇒ 2 unit - 1 unit = 40 unit

⇒ 1 unit = 40 unit

Usual time = 2 unit = 2 × 40 

Usual time = 80