Question

A number consists of two digits whose sum is 10. If 18 is subtracted form the number, its digits are reversed. Find the number.

Answer 1

Let the ones digit and tens digit be x and y respectively.
Then as per the question

x + y = 10                    …….(i)
(10y + x) – 18 = 10x + y
x –y = -2                    …….(ii)
Adding (i) and (ii), we get
2x = 8 ⇒ x = 4
Now, putting x = 4 in (i), we have
4 + y = 10 ⇒ y = 6
Hence, the number is 64.