Question

The tens digits of a two digit number is one more than thrice the unit digit. The sum of its digits is 9. Find the number.

Answer 1

Given:

• The tens digit of a two-digit number is one more than thrice the unit digit.
• The sum of its digits is 9.

Step-wise calculation:

Let the unit digit be (x).

Let the tens digit be (y).

From the problem:

1. The tens digit y = 3x + 1.
2. The sum of the digits x + y = 9.

Using equation (1) in (2):

x + (3x + 1) = 9 

4x + 1 = 9 

4x = 8 

x = 2

Find (y):

y = 3(2) + 1

y = 6 + 1 

y = 7

The number is:

10y + x = 10 × 7 + 2

10y + x = 70 + 2

10y + x = 72

The two-digit number is 72.