Gold For 7 days of Work

Puzzle Problem Statement

You’ve got someone working for you for seven days and a gold bar to pay him. The gold bar is segmented into seven connected pieces.

You must give them a piece of gold at the end of every day. What is the fewest number of cuts to the bar of gold that will allow you to pay him 1/7th each day?

Cut the gold bar and pay for 7 days

Solution Idea

We have only one gold bar and we have to pay equally for seven days. One obvious solution one can propose is 7 equal cuts in the golden bar and give 1/7 of the golden bar each day. But will that be the minimum? Think!

So let’s start from 1 Cut. It will give us 2 pieces of the gold bar. And to pay the worker on day 1, one will have to cut the first piece of size 1/7 and the rest will be 6/7. In such a case, we will not be able to pay the worker on day 2. So this doesn’t work.

Now moving forward with 2 Cuts. It will give us 3 pieces of gold bar. Let’s cut the pieces in such a manner so that one will be 1/7th of the whole gold bar, the second will be 2/7th of the whole gold bar, and the third will be 4/7th of the whole gold bar.

Cut the gold bar puzzle solution

Now try to pay for 7 days with these cuts.

Day 1: We give the 1/7th gold bar to the employee. Now there are two remaining gold bars of 2/7 and 4/7 size. Total Pay = 1/7.

Day 2: We give the 2nd bar of size 2/7 on the second day and take back the 1/7 sized bar to maintain equal pay each day. Now we will have 1/7 and 4/7 sized gold bars remaining. Total Pay = 2/7.

Day 3: We give the 1/7 sized bar on the third day. Now we will have 4/7 sized gold bars remaining. Total Pay = 3/7, (2/7 + 1/7).

Day 4: We give the 3rd bar of size 4/7 and take back both 1/7 and 2/7 sized bars. Now will have 1/7 and 2/7 sized bars remaining. Total Pay = 4/7.

Day 5: We give the 1/7 sized bar. Now we will be left with a 2/7 sized gold bar. Total Pay = 5/7 (4/7 + 1/7).

Day 6: We give the 2/7 sized bar and take back the 1/7 sized bar. Now we will have a 1/7 sized bar. Total Pay = 6/7, (4/7 + 2/7).

Day 7: On the final day, we give the last piece of a bar of size 1/7. Total Pay = 7/7 (4/7 + 2/7 + 1/7).

So in only 2 cuts, we have paid the employee in gold bars giving him equal pay each day. Hence minimum cuts that will be needed to pay equally for 7 days will be 2.

Enjoy learning, Enjoy algorithmic thinking!

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