Question

20. A train travels at 60 km/hr for 0.52 hr; at 30 km/hr for the next 0.24 hr and at 70 km/hr

for the next 0.71 hr. What is the average speed of the train?

Answer 1

hope it may help u nikki my frnd and pls reply

here , total dist = speed x time
 so , d = (60 x 0.52) + (30 x 0.24)+( 70 x 0.71)
=>d= 88.1 km
here ,total time taken will be 
t= 0.52+0.24+0.71 = 1.47 hrs
wkt , average speed = d/t 
=> 59.932 = 60 km/hr

Answer 2

Distance travelled in the 1st interval
=60 × 0.52=31.2km
Distance travelled in the 2nd interval
=30×0.24=7.2km
Distance travelled in the 3rd interval
=70×0.71=49.7km

Total distance travelled =88.1km
Total time taken to cover that distance = 1.47hr

So avg speed
= 88.1/1.47=59.93km/hr = 60 km/hr (approx)

Hope it helps..... :-)