Saved Bookmarks
| 1. |
Sitesh drove 12 hours at a speed of @ 75 km/hr. At present, how long should he drive at a speed of @ 90 km/hr so that the overall average speed will be 81 km/hr?1. 92. 7.53. 84. 6 |
|
Answer» Correct Answer - Option 3 : 8 Given : Sitesh drove 12 hours at a speed of @ 75 km/hr Concept used : Average speed = Total distance/Total time Calculations : Let the time taken for 90 km/h be 'x' Total distance = 75 × 12 + 90 × x ⇒ 900 + 90x Total time = (12 + x) hours According to the question The overall average speed is 81 km/h then, 81 = (900 + 90x)/(12 + x) ⇒ 81 × (12 + x) = 900 + 90x ⇒ x = 8 ∴ He drove for 8 hours at the speed of 90 km/h
|
|