Can You Solve This Money Doubling Puzzle with Chinku, Dinku, Pinku, and Tinku?

Hi,

Please solve it. Since your brain is fresh, you can work out the following puzzle.

This is a story of four boys - Chinku, Dinku, Pinku & Tinku. One day all of them decide to save their money in a bank, they select a bank called "Lena Bank."

The bank's specialty is: In every month, the money gets doubled. In the 2nd month, Chinku withdraws 100 Rs from the bank. In the 3rd month, Dinku withdraws 100 Rs from the bank. In the 4th month, Pinku withdraws 100 Rs from the bank. In the 5th month, Tinku withdraws 100 Rs from the bank, and their balance in the bank becomes zero.

How much amount had the boys put in the bank? The answer is the password of the Excel sheet. Give your brain cells some food. I have solved it. Now it's your turn!

Hey Swati,

I tried but I'm confused and not getting the answer. Can you please let us know the answer?

Thank you.

Hi all,

Just came across your names. I'm working on a project on performance appraisal methods in outsourcing companies. If any of you could give me some information, cheers! :)

Hi, I am Solv IT. Please find the attachment.

This is a story of four boys - Chinku, Dinku, Pinku & Tinku. - Yahoo! Answers India

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I have corrected the spelling and grammar errors in the user's input and formatted the text into a single paragraph.

At IIM, I was told that IITians solved such puzzles when they were at their mother's knees.

I had encountered this when I was in Standard VI (that is how it used to be written - in Roman numerals).

I had solved it in this manner:

Let the initial amount be x.

At the end of the first month, i.e., in the second month, the money would become 2x and considering Rs. 100 withdrawal, it will be: 2x-100

In the third month, the above amount will double, and considering Rs. 100 withdrawal, it will be: (2x-100)2 - 100

Similarly for the fourth month: {(2x-100)2 - 100}2 - 100

In the fifth month, after Rs. 100 withdrawal, it becomes zero. So, the equation for money in the bank will take the form: [{(2x-100)2 - 100}2 - 100]2 - 100 = 0

Solving the above:

[{(2x-100)2 - 100}2 - 100]2 = 100

or, [{4x-200 - 100}2 - 100]2 = 100

or, [8x-400 - 200 - 100]2 = 100

or, [8x-700]2 = 100

or, 16x-1400 = 100

or, 16x = 1500

or, x = 1500/16

or, x = 93.75

One of my classmates, who joined IIT later, chided me for taking lengthy intervening steps and suggested the following:

The total amount in the bank at the end of 4 months (beginning from the second month) would be: (x multiplied by 2 raised to power 4) - (2 raised to the power of 4 - 1)100 = 0

or, 16x - 1500 = 0

Solving for x, you get x = 93.75

Q.E.D.

Warm regards.