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Question
In a two-digit number, digit in units place is twice the digit in tens place. If 27 is added to it, digits are reversed. Find the number.
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Solution
Let ten’s digit of two-digit number be x.
Then unit’s digit = 2x
∴ Number = 10 × x + 2x
= 10x + 2x
= 12x
On reversing the digits,
New number = 10 × (2x) + x
= 20x + x
= 21x
12x + 27 = 21x
⇒ 21x – 12x = 27
⇒ 9x = 27
⇒ x = 3
Hence, the required number is 12 × 3, i.e. 36.
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