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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, 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 Saraswathi Vidyanikethan Pub School, added an answer, on 19/12/12
85 helpful votes in Math

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]

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