Narayan walking at a speed of 20 km/h reaches his college 10 minutes late. Next time he increases his speed by 5 km/h, but finds that he is still late by 4 minutes. What is the distance of his college from his house?
A. 10 km
B. 6 km
C. 12 km
D. 15 km
Answer: Option A
Solution (By Examveda Team)
By increasing his speed by 25%, he will reduce his time by 20%. (This corresponds to a 6 minutes drop in his time.) Hence, his time originally must have been 30 minutes. Thus required distance = 20 kmph × 0.5 hours = 10 km.This Question Belongs to Arithmetic Ability >> Speed Time And Distance
Assume that he should reach in x minutes
Let first he will reach in x + 10 minutes
Next time he will reach in x + 4 min
We know that distance = speed x time
In first case we get
distance = 20(x + 10)
= 20 x + 200
So in the second case
distance = 25 (x + 4)
= 25 x + 100
Equating both we get
20 x + 200 = 25 x + 100
5 x = 100
x = 20 min (actual time)
So in I case he will reach by x + 10 = 20 + 10 = 30 min
So in 1 hour he will travel 20 kms
So in 30 min he will travel 20 x 30 / 60 = 10 kms
Read more on Brainly.in - https://brainly.in/question/6020722#readmore
1st approach:
s=20:25
t=25:20=5:4=30:24
d=20/2=10 km/hr...(ans)
2nd approach:
20*25/25-20*1/10=10 km/hr
he will reduce his time by 20%...how you calculated this??