A 2-digit number is 3 times the sum of its digits. If 45 is

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RRB ASM Exam (Ajmer) 2007 click here to view all questions

A 2-digit number is 3 times the sum of its digits. If 45 is added to the number, its digits are interchanged. The sum of digits of the number is-

A11

B9

C7

D5

Nithin K ? Nov 20 '2016 at 19:27

Answer is : 9

Explanation:

A 2-digit number is 3 times the sum of its digits.
10y + x = 3(x + y)
10y + x = 3x + 3y
2x - 7y = 0 .........................(i)

If 45 is added to the number, its digits are interchanged.
10y + x + 45 = 10x + y
9x - 9y = 45 .......................(ii)

On Solving equation (i) and (ii)
x= 7
y= 2
number = 27
sum of the digits =(x+y)=(7+2)= 9

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Answer is : 9 Explanation: A 2-digit number is 3 times the sum of its digits. 10y + x = 3(x + y) 10y + x = 3x + 3y 2x - 7y = 0 .........................(i) If 45 is added to the number, its digits are interchanged. 10y + x + 45 = 10x + y 9x - 9y = 45 .......................(ii) On Solving equation (i) and (ii) x= 7 y= 2 number = 27 sum of the digits =(x+y)=(7+2)= 9 Nithin K ? answered Nov 20 '2016 at 19:27 All Comments

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