Question

A two digit number is obtained by either multiplying the sum of the digits by 8 then subtracting5 or by multiplyimg the difference by 16 and then adding 3 find the number

Answer 1

Solution :-

Let the two digit number be 10x + y where x is the tens digit and y is the ones digit.

Now, according to the question.
10x + y = 8(x + y) - 5
10x + y = 8x + 8y - 5
10x - 8x + y - 8y = - 5
2x - 7y = - 5 .................(1)

And,
10x + y = 16(x - y) + 3
10x + y = 16x - 16y + 3
10x - 16x + y + 16y = 3
- 6x + 17y = 3 ................(2)

Now, multiplying the equation (1) by 17 and (2) by 7, we get
34x - 119y = - 85 ...............(3)
- 42x + 119y = 21 ..............(4)

Now, adding (3) and (4), we get

34x - 119y = - 85
- 42x + 119y = 21
_________________
- 8x = - 64
_________________

⇒ 8x = 64
x = 64/8
x = 8
So, tens digit is 8.

Substituting the value of x = 8 in (1), we get
2x - 7y = - 5
2*8 - 7y = - 5
16 - 7y = - 5
- 7y = - 5 - 16
- 7y = - 21
7y = 21
y = 21/7
y = 3

Ones digit is 3.
So, the required number is 83.