if a boy walks at a speed of 10km/hr,he reach the destination 8min late. if he walks at 12km/hr he reached the destination 4 min early.. then what is the speed he can reach the destination at correct time??
Answers
Let the correct time be x hour
If he walks at 10km/h:
Distance = Speed x time
Distance = 10(x + 8/60) = 10x + 4/3
If he walks at 12km/h:
Distance = Speed x time
Distance = 12(x - 4/60) = 12x - 4/5
Solve x:
Since both the distance are the same
10x + 4/3 = 12x - 4/5
12x - 10x = 4/3 + 4/5
2x = 32/15
x = 32/15 ÷ 2
x = 16/15 hour
Find the distance:
Distance = Speed x Time
Distance = 12( 16/15 - 4/60) = 12 km
Find the speed:
Speed = Distance ÷ Time
Speed = 12 ÷ 16/15 = 11.25 km/hour
Answer: The boy needs to walk at 11.25 km/h to be just on time.
If he walks at 10km/h:
Distance = Speed x time
Distance = 10(x + 8/60) = 10x + 4/3
If he walks at 12km/h:
Distance = Speed x time
Distance = 12(x - 4/60) = 12x - 4/5
Solve x:
Since both the distance are the same
10x + 4/3 = 12x - 4/5
12x - 10x = 4/3 + 4/5
2x = 32/15
x = 32/15 ÷ 2
x = 16/15 hour
Find the distance:
Distance = Speed x Time
Distance = 12( 16/15 - 4/60) = 12 km
Find the speed:
Speed = Distance ÷ Time
Speed = 12 ÷ 16/15 = 11.25 km/hour