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A and B start simultaneously at 5 km per hr. and 4 km per hr. from P and Q, 180 kms apart, towards Q and P respectively. They cross each other at M and after reaching Q and P turn back immediately and meet again at N. Find the distance MN.
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- 45 km
- 40 km
- 35 km
- 42 km
Correct Option: B
When A and B cross each other at M for the first time, they have together covered the whole distance PQ = 180 km.
When they meet again at N, they have together covered total distance equal to 3 times of PQ = 3 × 180 = 540 km.
| PM = | × 180 = 100 km | |
| 5 + 4 |
[Distance covered by each will be in the ratio of their speeds)
| QP + PN = | × 540 = 240 km | |
| 5 + 4 |
or PN = 240 – QP = 240 – 180 = 60 km.
Then, MN = PM – PN
= 100 – 60 = 40 km.
