Question

Seven times a two-digit number is equal to four times the numbers obtained by reversing the order of its digits. If the difference between the digits of the given two digit number is 3, then the sum of digits of the number is:
1. 10
2. 9
3. 12
4. 11

Answer 1

Correct Answer - Option 2 : 9

Given:

x − y = 3

Calculation:

Let numbers be x at onces place & y at tens place so,

10y + x is the digit.

Reversed digit =10x + y

According to the question:

7(10y + x) = 4(10x + y)

⇒ x = 2y      ----(1)
Now,

From equation (i) 2y = x substitute in above equation:

2y − y = 3

⇒ y = 3
So , 
x = 2y = 2 × 3 = 6

Original number is =10y + x = (10 × 3 + 6) = 36

Sum of number = 3 + 6 = 9

∴ The sum of digits of the number is 9.