Question

A man earns Rs. 20 on the first day and spends Rs. 15 on the next day. He again earns Rs. 20 on the third day and spends Rs. 15 on the fourth day. If he continues to save in this way, how soon will he have Rs. 60 in hand?
A. On 12th day
B. On 24th day
C. On 17th day
D. On 27th day

Answer 1

Hint: We will start by using the fact that savings is equal to expenditure subtracted from total income. We will then find the saving of the man in 2 days' combination to find the time he takes for saving Rs. 60.

Complete step-by-step answer:
Now, we have been given that a man earns Rs. 20 on the first day and spends Rs. 15 on the next day and continues to spend in this way.
Now, we know that,
Savings = Income – Expenditure
Now, we have the savings of man in first 2 days,
$\begin{align}
  & =20-15 \\
 & =5 \\
\end{align}$
Now, the man will save money in the next two days and that will also be Rs. 5.
So, effectively in 2 days the man is able to save Rs. 5.
So, now, to find how many batches of 2 days the man will take to save Rs. 60. We will divide 60 by 5. So, we have,
$\begin{align}
  & =\dfrac{60}{5} \\
 & =12 \\
\end{align}$
Now, 12 batches 2 days will be required to save Rs. 60, this means that the man will have Rs. 60 in hand in $12\times 2={{24}^{th}}day$.
Hence, the correction option is (B).

Note: It is important to note that we have first found the collective saving of the many for 2 days batch and use it to find how many such batches the man will take to save Rs. 60 and used this fact to find the day on which he will have Rs. 60 in hand.