Akash travels from D to S at the speed of 15 km/h , from S to X at 30 km/h and from X to Z at 45 km/h. If DS = SX = XZ = 90 (in km) , then the average speed of Akash for the whole journey is:
Answer & explanation
Correct answer: option 3
Let, DS (D1) = SX (D2) = XZ (D3) = 90 km
T1 = \(\frac{D_1}{S_1}\) = \(\frac{90}{15}\) = 6 hours
Similarly,
T2 = \(\frac{90}{30}\) = 3 hours
T3 = \(\frac{90}{45}\) = 2 hours
Total time = T1 + T2 + T3 = 6 + 3 + 2 = 11 hours
Total distance = D1 + D2 + D3 = 90 + 90 + 90 = 270 km
Average speed =\(\frac{total\;distance}{total\;time}\)
= \(\frac{270}{11}\) = 24 \(\frac{6}{11}\) km/h