Abus takes 2 hrs less for a journey of 300 km, if its speed is increased by 5km/hr from its usual speed, then the usual speed in km/hr is

Let the usual speed of bus be x km/hr.

Time = Distance / Speed = 300/x hrs

According to the question,

=> (300/x - 2) (x + 5) = 300

=> (300 - 2x)/x (x + 5) = 300

=> 300x + 1500 - 2x² - 10x = 300x

=> 2x² + 10x - 1500 = 0

=> 2(x² + 5x - 750) = 0

=> x² + 30x - 25x - 750 = 0

=> x(x + 30) - 25(x + 30) = 0

=> (x - 25) (x + 30) = 0

=> x = 25 or x = - 30

∴ x ≠ - 30 (Because speed can't be negative)

Hence,

The usual speed of bus = 25 km/hr

7. d. 64

8. i. 32

9. c. 125

10. j. none of the above

11. d. 81

12. i. 216

13. e. none of the above

14. g. 240

15. e. none of the above

16. g. 32

17.   e. none of the above