A number consists of two digits whose sum is 8. If 18 is subtracted from the number, the place of digits get interchanged. Find the number.

• A. 32
• B. 53
• C. 46
• D. 35

Answer: (B)

Suppose the digit at unit's places is y and that at ten's places is x.Then, the number = 10x + y,According to the question.x + y = 8 .......(i)Again 10x + y - 18= 10y + x= 10x + y - 10y - x = 18= x - y = 2 ............(iii)From, equation (i) and (iii) we get x + y = 8x - y = 22x = 10= x = 5 and y = 3∴ number = 10 x 5 + 3 = 53