Question

Plssss answer this question and i'll mark the correct one as the brainliest .


A boy runs for 10 min . at a uniform speed of 9 km/h . at what speed should he run for next 20 min so that the average speed comes out to be 12km/h.

Answer 1

HeY !!!



speed of boy for 10 min is 9km/h
time :- 10min = 10/60 = 1/6hour

so , distance = speed ×time

=> 9×10/60 = 9/6 = 3/2km


•°• total time = 20 m = 20/60 = 1/3 hour

here given average speed * = 12km/h

Average speed = average distance/total time taken

12 = 3/2 + x/

12× = 3/2+ x/1/3

12×1/3 = 3 + 2x /2

4 ×2 = 3+2x

8 -3 = 2x

5 = 2x

x = 5/2 km

means after 10min at speed 9km/h boys cover 5/2km in time 10 min

hence after 10 min in fensing 10 min =1/6hour

speed = 5/2/1/6

speed = 15km/h

if boy run 15km/h after 10min in 10min then average speed should be 12km/h

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Hope it helps you !!!

@Rajukumar111
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