The digit in the unit 39 s place of a numbers is equal to the digit in the ten 39 s place of half of...........

Quantitative Aptitude ( CCS) Number System

The digit in the unit's place of a numbers is equal to the digit in the ten's place of half of that number and the digit in the ten's place of that number is less than the digit in unit's place of half of the number by 1. If the sum of the digits of the number is 7, then what is the number ?

None of these

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Explanation:

Let the digit in units place be y
the digit in tens place be x
Then, number is 10x + y
Digit in the tens place of half of the number =y
Digit in the units place of half of the number = (x+1)
Therefore, half of the number = 10y+(x+1)

(10x+y)/2 = 10y+x+1
10x+y = 20y+2x+2
8x−19y = 2 <==equation 1

x+y=7
(x+y=7)8

8x + 8y = 56 <==equation 2

8x + 8y = 56
- (8x−19y = 2)
______________

27y = 54

y = 2

x=7− y

x=7 - 2

x = 5
The number is 52.

Hence, option 2 is the correct answer.