A man walked at a speed of 9km/h from point A to B and came back from point B to A at a speed of 15km/h. The ratio of the time taken by the man in walking from B to A to that from A to B was:
- A7 : 2
- B5 : 3
- C3 : 5
- D2 : 7
Solution & Step-by-step Explanation
Let the distance between points A and B be d.
Speed from A to B (S
AB
) = 9km/h
Time taken from A to B (T
AB
)=
9
d
Speed from B to A (S
BA
) = 15km/h
Time taken from B to A (T
BA
)=
15
d
We need to find the ratio of the time taken from B to A (T
BA
) to that from A to B (T
AB
):
T
AB
T
BA
=
9
d
15
d
=
15
9
=
5
3
Thus, the required ratio is 3:5.
Alternative Method:
Since distance is constant, time is inversely proportional to speed (T∝
S
1
).
T
AB
T
BA
=
S
BA
S
AB
=
15
9
=
5
3
Speed from A to B (S
AB
) = 9km/h
Time taken from A to B (T
AB
)=
9
d
Speed from B to A (S
BA
) = 15km/h
Time taken from B to A (T
BA
)=
15
d
We need to find the ratio of the time taken from B to A (T
BA
) to that from A to B (T
AB
):
T
AB
T
BA
=
9
d
15
d
=
15
9
=
5
3
Thus, the required ratio is 3:5.
Alternative Method:
Since distance is constant, time is inversely proportional to speed (T∝
S
1
).
T
AB
T
BA
=
S
BA
S
AB
=
15
9
=
5
3