RRB Group-D Model Paper 11 with answers for online practice

Let the digit on one’s place be y and the digit in ten’s place be x
∴ The number is = 10x + y
Sum of the digits is 10
∴ x + y = 10
Now, when 18 is added, the digits are reversed
∴ New number = 10y + x
∴ (10x + y) + 18 = 10y + x
⇒ 9x + 18 = 9y
⇒ x + 2 = y
∴ x + y = 10
⇒ x + (x + 2) = 10
⇒ 2x + 2 = 10
⇒ 2x = 8
⇒ x = 4
∴ y = 10 – x = 10 – 4 = 6
∴ The number is 10x + y = (10 × 4) + 6 = 46