Ramesh, on his way to his hometown, travelled the first 250 km at a speed of 75 km/h and the next 250 km at a speed of 85 km/h. Find the average speed for the whole journey(correct to 2 decimal places).

Question

Question

This question was previously asked in

SSC CGL 2023 Tier-I Official Paper (Held On: 25 Jul 2023 Shift 2)

Answer 1

Given:

Speed of Ramesh for 1st 250 km = 75 km/h

Speed of Ramesh for 2nd 250 km = 85 km/h

Formula used:

Average speed = Total distance/total time taken

Calculation:

Total distance = 250 + 250 = 500 km

Total time taken = (250/75) + (250/85)

⇒ 250 × (1/75 + 1/85)

⇒ 250 × {(17 + 15)/1275}

⇒ 320/51

Average speed = Total distance/total time taken

⇒ 500/(320/51) = (500 × 51)/320

⇒ (25 × 51)/16 = 79.68 km/h

∴ The correct answer is 79.68 km/h.

Alternate MethodCalculation:

Now,

Average speed = (1275 × 2)/(17 + 15)

⇒ 2550/32 = 1275/16 = 79.68 km/h

∴ The correct answer is 79.68 km/h.