Question

The tens digit in a two digit number is twice the unit’s digit . If 18 is subtracted from the number, the digits are reversed. Find the number.

Answer 1

Let,the digit in unit's place be x.
Thus,digit in ten's place is twice,i.e. 2x.
Hence,the no. is (2x ×10 + x)
= 21x
According to the problem,

21x - 18 = 10x + 2x
or,21x - 18 = 12x
or,21x - 12x = 18
or,9x = 18
or,x = 2

Therefore, digit in unit's place is 2.
Thus,digit in ten's place is 2×2 = 4.
The number is 42.

This problem can also be solved by framing Simultaneous linear equations( two variables ).

Answer 2

Answer:

Number is 2

Step-by-step explanation:

Let the units digit=x

Then the tens digit=2x

Number is 10×(2x)+x

On reversing ,

New number 10(x)+2x

Given,

10×(2x) +x -18=10×(x)+2x

20x+x-18=10x+2x

21x-18=12x

9x=18

x=2

The original number is

10×(2x)+x

=10(2×2) + 2

=42