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Mathematics

The sum of a two digit number and the number obtained by reversing the order of the digits is 99. Find the number, if the digits differ by 3.

Linear Equations

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Answer

Let digit at ten's place be x and unit's place be y.

Number = 10(x) + y = 10x + y

On reversing the digits,

Reversed number = 10(y) + x = 10y + x

Given,

Sum of a two digit number and the number obtained by reversing the order of the digits is 99.

∴ (10x + y) + (10y + x) = 99

⇒ 11x + 11y = 99

⇒ 11(x + y) = 99

⇒ x + y = 9

⇒ x = 9 - y …………(1)

Given,

Digits differ by 3.

∴ x - y = 3 or y - x = 3

Considering x - y = 3

⇒ x = 3 + y ……….(2)

From (1) and (2), we get :

⇒ 9 - y = 3 + y

⇒ 9 - 3 = 2y

⇒ 2y = 6

⇒ y = 3.

Substituting value of y = 3 in equation (1), we get :

⇒ x = 9 - 3 = 6.

Number = 10x + y = 10(6) + 3 = 60 + 3 = 63.

Considering y - x = 3

⇒ x = y - 3 ……….(3)

From (1) and (3), we get :

⇒ 9 - y = y - 3

⇒ 9 + 3 = 2y

⇒ 2y = 12

⇒ y = 6.

Substituting value of y = 6 in equation (1), we get :

⇒ x = 9 - 6 = 3.

Number = 10x + y = 10(3) + 6 = 30 + 6 = 36.

Hence, number = 36 or 63.

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