Question 54

Logical Reasoning Number representations Hard

Using only 2, 5, 10, 25 and 50 paise coins, what is the smallest number of coins required to pay exactly 78 paise, 69 paise and Rs. 1.01 to three different persons?

(A) 19
(B) 20
(C) 17
(D) 18
View Dynamic Solution & Explanation
Correct Solution: Option A

Step-by-step Solution:

Quick Solution

The goal is to pay three separate amounts using the smallest possible total number of coins. To achieve this, we should use a "greedy" approach for each amount: use as many of the largest value coins as possible for each payment.

Available coin denominations: 50 paise, 25 paise, 10 paise, 5 paise, and 2 paise.


1. Paying 78 paise

To make 78 paise with the minimum number of coins:

  • 1 × 50p (Leaves 28p)
  • 2 × 10p (Leaves 8p)
  • 4 × 2p (Leaves 0p)

Total coins for 78p = 1 + 2 + 4 = 7 coins.


2. Paying 69 paise

To make 69 paise with the minimum number of coins:

  • 1 × 50p (Leaves 19p)
  • 1 × 10p (Leaves 9p)
  • 1 × 5p (Leaves 4p)
  • 2 × 2p (Leaves 0p)

Total coins for 69p = 1 + 1 + 1 + 2 = 5 coins.


3. Paying Rs. 1.01 (or 101 paise)

To make 101 paise with the minimum number of coins:

  • 1 × 50p (Leaves 51p)
  • 1 × 25p (Leaves 26p)
  • 2 × 10p (Leaves 6p)
  • 3 × 2p (Leaves 0p)

Total coins for 101p = 1 + 1 + 2 + 3 = 7 coins.


4. Total Number of Coins Required

The smallest total number of coins required is the sum of the coins for each separate payment.

7 (for 78p) + 5 (for 69p) + 7 (for 101p) = 19 coins

Final Answer: The smallest number of coins required is 19.