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Aryan A. from INDIAN MODEL SCHOOL , asked a question
Subject: Math , asked on 19/12/12

IN A 2DIGIT NO., TEN 'S DIGIT IS TWICE THE UNIT 'S DIGITS. THE NO. FORMED BY INTERCHAMGING THE DIGITS IS 36 LESS THAN THE ORIGINAL NO.. THE NO. IS.............?

EXPERT ANSWER

Manish Bharti ,Meritnation Expert added an answer
Answered on 21/12/12

Let the unit digit be x. 
then, the ten 's digit is 2x
and the number is
By interchanging the digits, 10 's digit becomes x and unit digit becomes 2x
New number
According to the question,

Therefore, the number is 84

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Srinidhi D. Pai , From Chinmaya Vidyalaya , added an answer
Answered on 19/12/12

Let the unit digit be x. So the ten 's digit is 2x

The value of the number is 10*2x + x = 20x + x = 21x

By interchanging the digits, 10 's digit is x and unit digit is 2x

New value = 10*x + 2x = 12x

Original value - new value = 21x - 12 x = 9x

But it is given that the difference is 36

so 9x = 36

x = 36/9 = 4

2x = 8

so the number is 84

[check answer: 84 - 48 = 36; so ok]