**Q.**

**Quiz time:-**

**A very interesting puzzle.**

**Lets see who solves this.**

**Four friends A, B, C, D **

**Need to cross a bridge..**

**A maximum of 2 peoples can cross at a time..**

**It is night and they have just 1 lamp.**

**People that cross the bridge must carry the lamp to see the way..**

**A pair must walk together at the speed of slower person…**

**Speeds of**

**A: 1 minute to cross bridge**

**B: 2 minutes to cross bridge**

**C: 9 minutes to cross bridge**

**D: 10 minutes to cross bridge**

**Now question is…**

**“what is the total minimum time required by all 4 friends to cross the bridge….?”**

**Ans is:**

A+B cross with lamp => 2 min

A comes back with lamp => 1 min

C+D cross with lamp =>10 min

B comes back with lamp => 2 min

A+B cross with lamp => 2 min

Total 2+1+10+2+2 = 17 min

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A+D cross with lamp => 10 min

A comes back with lamp => 1 min

A+C cross with lamp =>9 min

A comes back with lamp => 1 min

A+B cross with lamp => 2 min

Total 10+1+9+1+2 = 23 min

Is it correct?

Sorry, its wrong answer ! Its much lower π

Sorry, its wrong answer ! Its much lower :). How about A and B go together?

They do go together once. Considering the conditions mentioned – “People that cross the bridge must carry the lamp to see the way. And a pair must walk together at the speed of slower person”, I think the fastest person should be the one to do all the running with the lamp. So A will accompany 2 of the others and come back with lamp and cross the bridge with the last person.

Hint , A and B go together first

Hey Soumya, We have updated the answer now. You were close π

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My answer was not close! π But yeah..good solution. I like your puzzles π

Glad to know you like our puzzles . Cheers !

15 mins

Thanks for the reply, can you elaborate the answer please ?