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Advanced Math/Average Speed question

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Question
Salam.
I have a Speed/Distance/Time question for IGCSE. The question is: A car travels for 60 km at 30 km/h and then a further 180 km at 160 km/h.
(a)Find the total time taken
(b)Find the average speed for the whole journey.
Thank you in advance.

Answer
Hi Hanaa,
a) We know that Speed = Distance / Time
So, Time = Distance / Speed
When the car travels 60km at 30km/h it takes a time of
60/30 = 2 hours
and when it travels 180km at 160km/h it takes a time of
180/160 = 1.125 hours

The total time taken is therefore 2 + 1.125 = 3.125 hours
Note that if you so require you can convert the decimal part into minutes by multiplying by 60.
0.125 hours = 0.125 x 60 mins = 7.5 minutes
and the total time is 3 hours and 7.5 minutes.

b) The total distance covered = 60km + 180km = 240km
The total time taken = 3.125 hours
Average Speed = Total Distance / Total Time
= 240 / 3.125
= 76.8 km/h

Regards

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