15. A person completes 30 km of a journey at 6 km/hr and the remaining 60 km in 7 hours. Find his average speed
the whole journey.
a) 9 km/hr
b) 10 km/hr.
c) 8.4 km/hr
d) 7.5 km/hr.
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1
Answer:
d) 7.5 kmph
Step-by-step explanation:
The person covers 30 km at the speed of = 6kmph .
Hence the time taken to cover 30 km =
= distance /speed
= 30 km / 6kmph = 5 hours
He covers first 30 km in 5 hours .
He covers remaining 60 km in 7 hours .
Total distance covered = 30km + 60km
= 90km
Total time taken to cover = 5hours + 7hours
= 12 hours
Average speed = Total distance / Total time
= 90km / 12 hours
= 7.5 kmph
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