Two Kids Alyse, Jeremy and their Grandpa and Grandma were going to the train sta

Question

Two Kids Alyse, Jeremy and their Grandpa and Grandma were going to the train station to catch a train. Before they could get to the station, they must cross a river through a narrow bridge. It was a dark evening and the bridge was very dangerous to use without lights. Fortunatley, Grandpa had a pocket flashlight but it was just bright enough for at most two people to use at a time. The bridge was also not short enough for them to throw the flashlighbt back, so one must carry the flashlight back for the other two people to use.

Alyse could cross in 2 Minutes

Jeremy could cross in 1 minute

Grandpa needed 10 minutes to cross

Grandma needed 5 minutes

If two people were walking together, the faster one must slow down for the slower one because no body was strong enough to carry another person. The train was going to leave in 18 minutes, yet they managed to cross the river in 17 minutes.

How did they do that.

Draw diagram. Explain Complete process/ each step.

Explanation / Answer

Solution:

Given that

Alyse could cross in 2 Minutes

Jeremy could cross in 1 minute

Grandpa needed 10 minutes to cross

Grandma needed 5 minutes

they have only 17 minutes in their hands

therefore we have to minimize the time in order to cross the river

Since Jeremy could cross in 1 minute

hence we take him as the one who would help in crossing all other three family member

Now .,

1st step

time taken when Alyse and Jeremy cross river = 2 minute ( Alyse take longer time than Jeremy )

and now Alyse time taken in returning back alone of leaving back Jeremy on other shore = 2 minute

total time taken for 1st crossing = 2+2 = 4 minute

2st step

time taken when Grandpa and Grandma cross river = 10 minute ( Grandpa take longer time than Grandma )

and Jeremy would return back hence time taken in returning back alone of leaving back Grandpa and Grandma on other shore = 1 minute

total time taken for 2nd crossing = 10+1 = 11 minute

3rd step

time taken when Alyse and Jeremy cross river = 2 minute ( Alyse take longer time than Jeremy )

SInce all people crossed in above 3 step

therefore total time taken in these three steps = 4 + 11 + 2 =17 minute

hence they managed to cross the river in 17 minutes

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