The digit at ones place of a two digit number is three times the digit at tens place. When 54 is added to the number its digit are reversed. Find the number

The number is 39

Step-by-step explanation:

Let the number at the tens place be x and the number at ones place be y.

Hence, The number is 10x + y.

From the question, the digit at ones place (y) is three times the digit at tens place (x). That is, y is three times x. This means

y = 3x (1)

Also, When 54 is added to the number, its digits are reversed (That is, the resulting number would be 10y + x). This means

10x + y + 54 = 10y + x (2)

Put the value of y = 3x from equation (1) into equation (2) to solve for x

Then,

10x + y + 54 = 10y + x

10x + 3x + 54 = 10(3x) + x

13x + 54 = 30x + x

13x + 54 = 31x

31x - 13x = 54

18x = 54

x = 54/18

x = 3.

Now, Put the value of x = 3 into equation (1) to solve for y

y = 3x

y = 3(3)

y = 9.

Hence, x = 3 and y = 9.

Since the number is 10x + y

Substitute the values of x and y.

Then,

10x + y = 10(3) + 9

=30 + 9

= 39

Hence, the number is 39.