NIMCET 2020 Question Paper with solutions

Question : 52 of 120

Marks: +1, -0

Four friends A, B, C and D need to cross a bridge in the night. A maximum of 2 people can cross at a time. They have only one lamp. A takes one minute to cross the bridge. B takes 2 minutes, C takes 8 minutes and D takes 11 minutes to cross the bridge respectively. A pair must walk together at the speed of the person who walks slowly. What is the minimum time required to cross the bridge by all the four people?

23 minutes
20 minutes
18 minutes
16 minutes

Validate

Solution:

Step 1: A and B cross the bridge with the lamp.(2 mins)
Step 2: A comes back with the lamp.(1 mins)
Step 3: C and D cross the bridge with the lamp .(11 mins)
Step 4: B brings back the lamp.(2 mins),
Step 5: A and B cross the bridge with lamp.(2 mins)
Total minimum time required

=2+1+11+2+2=18 \mins

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