The sum of two digits of a number is 10. If the digits are interchanged, then its value increases by 18. Find the number.

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RRB Non Technical Exam (Secunderabad) 2016 click here to view all questions

The sum of two digits of a number is 10. If the digits are interchanged, then its value increases by 18. Find the number.

A46

B64

C19

D28

rahim ? Jan 10 '2020 at 12:0

Correct answer is: 46

Explanation:

Let us assume the digits are x and y, so the number is written as "xy".

Sum of digits is 10, so

x + y = 10 ..........................(1)

as x is in 10s' place and y in units place the actual number is 10*x + y

when the digits are interchange (i.e number written as "yx") the actual number becomes 10*y+x

Given that interchanging increases the value by 18, so

(10*y+x) - (10*x + y) = 18

i.e 9*y - 9*x = 18

i.e y - x = 2 ............................. (2)

Adding (1) and (2) we get

2*y = 12

or y =6

Putting y = 6 in (1)

x + 6 = 10

or x =4

So the number is 10*x + y

i .e 10 * 4 + 6

or 46

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Correct answer is: 46 Explanation: Let us assume the digits are x and y, so the number is written as "xy". Sum of digits is 10, so x + y = 10 ..........................(1) as x is in 10s' place and y in units place the actual number is 10*x + y when the digits are interchange (i.e number written as "yx") the actual number becomes 10*y+x Given that interchanging increases the value by 18, so (10*y+x) - (10*x + y) = 18 i.e 9*y - 9*x = 18 i.e y - x = 2 ............................. (2) Adding (1) and (2) we get 2*y = 12 or y =6 Putting y = 6 in (1) x + 6 = 10 or x =4 So the number is 10*x + y i .e 10 * 4 + 6 or 46 rahim ? answered Jan 10 '2020 at 12:0 All Comments

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