Question

A train covered first 120km at speed of 5okm /h and then covered the remaining 280km at speed of 80km/hr. find it's average speed.​

Answer 1

Answer:

(i) time = distance / speed

= 120 km/ 50 km / hr

= 2.4 hr

(ii) time = 280km/ 80 km/ hr

= 3.5 hr

average speed = total distance covered / total time taken

= 120km + 280km / 2.4 hr + 3.5 hr

= 400km / 5.9 hr

= 67.79 km/ hr

hope it helps you

Answer 2

Explanation:

average speed = total distance / total time

now

v1 = 50km/hr

d1 = 120 km

v1 = d1/t1

50 = 120/ t1

t1 = 120/ 50 = 12/ 5 hr = 2.4 hr

v2 = 80km/hr

d2 = 280 km

v2 = d2/t2

80 = 280/t2

t2 = 280/80 = 28/8 = 3.5 hr

now total time = t1 + t2 = 2.4+ 3.5 = 5.9 hr

total distance = d1 + d2 = 280km + 120km = 400km

now average speed = 400/5.9 = 67.79 km/ hr