SOLUTION: Hi
Guan heng left P and drove at 72kmph for 45 min. Then he increased his speed to 84kmph and drove for a further 40mins prior to reaching his home. His sister left P 20min earlie
Algebra.Com
Question 1170496: Hi
Guan heng left P and drove at 72kmph for 45 min. Then he increased his speed to 84kmph and drove for a further 40mins prior to reaching his home. His sister left P 20min earlier than him but she reached her home 25 min later.
What was his sisters average speed
Answer by Theo(13342) (Show Source): You can put this solution on YOUR website!
rate * time = distance
72 kmph * 45/60 hours = 54 kilometers.
84 kmph * 20/60 hours = 56 kilometers.
total distance is 110 kilometers.
total time is (45 + 40) / 60 = 85 / 60 = 1.4166666667 hours.
average speed is 110 kilometers / 1.4166666667 = 77.64705882 kmph.
she left 20 minutes earlier and arrived 25 minutes later.
her time for the trip was (20 + 45 + 40 + 25) = 130 minutes / 60 = 2.166666667 hours.
her average speed was 110 / 2.166666667 = 50.76923077 kmph.
you could do this with fractions and should get the same answer.
doing it with fractions, you get:
72 kmph for 45/60 hours = a distance of 54 kilometers.
84 kmph for 40/60 hours = a distance of 56 kilometers.
total distance is 110 kilometers.
total time is 85/60 hours.
she started 20 minutes earlier and arrived
25 minutes later.
it took her a total time of 85 + 45 = 130/60 hours.
her average speed was 110 / (130/60) = 110 * 60 / 130 = 6600/130 kmph.
6600/130 = 50.76923077 kmph.
it's the same answer done with fractions for the intermediate calculations.
RELATED QUESTIONS
Can anyone help me with this word problem:
Hanson drove his rig at x mph for 3 hours,... (answered by Earlsdon)
Richard drove his rig at ‘x’ mph for 3 hours, then increased his speed to (x + 15) mph... (answered by funmath)
Travel problems I just don't understand. Richard drove his rig at 'x' mph for 3 hours,... (answered by jejess)
Richard drove his rig at ‘x’ mph for 3 hours, then increased his speed to (x + 15) mph... (answered by drj)
Richard drove his rig at ‘x’ mph for 3 hours, then increased his speed to (x + 15) mph... (answered by ankor@dixie-net.com)
Steve Forrester drove 25 miles at a constant speed,and then he increased his speed by 15... (answered by josgarithmetic,ikleyn)
For 4 hours Sam traveled at 40 miles per hour. Then he increased his speed to 60 miles... (answered by tommyt3rd)
Greg drove at a constant speed in a rainstorm for 280 miles. He took a break, and the... (answered by richwmiller)
Greg drove at a constant speed in a rainstorm for 294 miles. He took a break, and the... (answered by josmiceli,MathTherapy)