Correct Answer - Option 3 : 13.36 km
Given:
Average speed of bus for the whole journey is 25 km/hr.
28 km are travelled at the speed of 22 km/hr and rest at 35 km/hr.
Concepts used:
Average speed = S1 × S2 × (d1 + d2)/(S1d2 + S2d1)
Calculation:
A bus covered 28 km at the speed of 22 km/hr and rest distance at the speed of 35 km/hr.
Average speed = S1 × S2 × (d1 + d2)/(S1d2 + S2d1)
⇒ 25 km/hr = 22 × 35 × (28 + x)/(22 × x + 35 × 28) km/hr
⇒ 25 = 770 × (28 + x)/(22x + 980) km/hr
⇒ 25 × (22x + 980) = 770 × 28 + 770x
⇒ 25 × 22x + 25 × 980 = 21,560 + 770x
⇒ 550x + 24,500 = 21,560 + 770x
⇒ 770x - 550x = 24,500 - 21,560
⇒ 220x = 2,940
⇒ x = 2,940/220 km
⇒ x = 13.36 km
∴ Remaining distance travelled by bus is equal to 13.36 km.
