Question

Two  bikes A and B  start from one point and move along two roads at right angles to each other. If their speeds be respectively 42 km/hr and 56 km/hr, then after 30 minutes they will be x km apart. What is x ?

1. 35 km
2. 40 km
3. 45 km 
4. 50 km 
5. None of these

Answer 1

Correct Answer - Option 1 : 35 km

Given that:

Speed of first bike A= 42 km/hr

Speed of second bike B = 56 km/hr

Time = 30 minutes = ½ hour

Formula:

Distance = speed × time

Calculation:

Distance covered by bike A = 42 × 1/2 = 21 km

Distance covered by bike B = 56 × 1/2 = 28 km

Now, both of them are x km apart  after 30 minutes

Both the bikes are moving along the right angles to each other,

we have,

⇒ 21² + 28² = x²

⇒ 441 + 784 = x²

⇒ 1225 = x²

⇒ x = 35

∴ After 30 minutes, these two bikes will be 35 km apart