# Aptitude - Problems on Numbers - Discussion

Discussion Forum : Problems on Numbers - General Questions (Q.No. 4)
4.
The difference between a two-digit number and the number obtained by interchanging the digits is 36. What is the difference between the sum and the difference of the digits of the number if the ratio between the digits of the number is 1 : 2 ?
4
8
16
None of these
Explanation:

Since the number is greater than the number obtained on reversing the digits, so the ten's digit is greater than the unit's digit.

Let ten's and unit's digits be 2x and x respectively.

Then, (10 x 2x + x) - (10x + 2x) = 36

9x = 36

x = 4.

Required difference = (2x + x) - (2x - x) = 2x = 8.

Discussion:
45 comments Page 5 of 5.

Nathi said:   1 decade ago
At first we should decide the digits of 10's & unit's be X & 2X respectively.
((10 x 2X) + X) - ((10 x X) + 2X) = 36
(20X + X) - (10X + 2X) = 36
21X - 12X = 36
9X = 36
X = 4
The difference between two digits = (2X+X)-(2X-x)
= 3X - X
= 2X
= 2(4)
= 8
(2)

Sravanthi said:   1 decade ago
Hi I can't understand this problem. Any more explnation please.
(1)

Sikha said:   1 decade ago
It can't b (x+y) - (x-y).

Rather it could be (10x +y) - (10y + x).
(1)

Pavithra said:   1 decade ago
I get the answer as 16.

Diff in digits: (x+y)-(x-y)

=2y
=2(2x)
=4x.

Finding the value of x we get, x=4;

So ans = 4(4) = 16.

Ramya said:   1 decade ago
Hi I could not understand this problem. Can anyone explain this more clearly please?
(1)