Question

A bus maintains an average speed of 60 km/hr while going from Pto Q and maintains an average speed
of 90 km/hr while coming back from Q to P. The average speed of the bus is
O 75 km/h
0 72 km/hr
O 70 km/hr
O 30 km/h​

Answer 1

The answer is 75 km/h.

Please mark me as *BRAINLIST*.

Answer 2

Answer:

The average speed of the bus is 72 km/hr.

Step-by-step explanation:

Given :-

• A bus maintains an average speed of 60 km/hr while going from P to Q and maintains an average speed of 90 km/hr while coming back from Q to P.

To find :-

• Average speed of the bus.

Solutuon :-

Let the distance between P and Q be x km.

★Formula used :

${\boxed{\sf{Time=\dfrac{Distance}{Speed}}}}$

Then,

Time taken by bus from P to Q (t) = x/60 hr

&

Time taken by bus from Q to P (t') = x/90 hr

Total distance covered = x+x = 2x km

&

Total time taken,

= t + t'

= [(x/60 + x/90) ] hr

= [(3x+2x)/180 ] hr

= 5x/180 hr

= x/36 hr

★ Formula used :

${\boxed{\sf{Average\: Speed=\dfrac{Total\: distance\: covered}{Total\: time\: taken}}}}$

$: \implies \sf \: Average \: speed = \dfrac{2x}{ \dfrac{x}{36} } \: \: km/ hr \\ \\ : \implies \sf\: Average \: speed \: = \dfrac{2x \times 36}{x} km/hr \\ \\ : \implies \sf \: Average \: speed \: = 72 \: km/hr$

Therefore, the average speed of bus is 72 km/hr.