A number consists of two digits whose sum is 9. If 9 is subtracted from the number, the digits interchange their places. The number is?

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RRB TA Exam (Malda) 2008 click here to view all questions

A number consists of two digits whose sum is 9. If 9 is subtracted from the number, the digits interchange their places. The number is?

A44

B54

C62

D53

rajavardhan ? Jul 2 '2017 at 10:29

Answer is 54

Explanation:

Let us assume, x and y are the two digits of a two-digit number.
Therefore, the two-digit number = 10x + y and the reversed number = 10y + x

Given:
x + y = 9 ---------1

Also given:
10x + y - 9 = 10y + x
9x - 9y = 9
x - y = 1 -----------2

Adding equation 1 and equation 2
2x = 10
x = 5

Therefore, y = 9 - x = 9 - 5 = 4

Therefore, the two digit number = 10x + y = 10*5 + 4 = 54

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Answer is 54 Explanation: Let us assume, x and y are the two digits of a two-digit number. Therefore, the two-digit number = 10x + y and the reversed number = 10y + x Given: x + y = 9 ---------1 Also given: 10x + y - 9 = 10y + x 9x - 9y = 9 x - y = 1 -----------2 Adding equation 1 and equation 2 2x = 10 x = 5 Therefore, y = 9 - x = 9 - 5 = 4 Therefore, the two digit number = 10x + y = 10*5 + 4 = 54 rajavardhan ? answered Jul 2 '2017 at 10:29 All Comments

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