Let x be a two-digit number. If the sum of the digits of x is 9, then

Question

Let x be a two-digit number. If the sum of the digits of x is 9, then the sum of the digits of the number (x + 10) is

(A) 1

(B) 8

(C) 10

(D) either 8 or 10

(E) either 1 or 10

BrentGMATPrepNow · Accepted Answer

One approaches to examine the  extremes ...

18 is the smallest possible value of x. 
So, x + 10 = 18 + 10 = 28
2 + 8 = 10
So, the correct answer is either C, D or E

90 is the biggest possible value of x. 
So, x + 10 = 90 + 10 = 100
1 + 0 + 0 = 1
So, the correct answer is E

chrisjonatan · Answer

Sum of digit
A + B = 9

A + B can be:
1 + 8
2 + 7
3 + 6
4 + 5
5 + 4
6 + 3
7 + 2
8 + 1
9 + 0

If x = 18, X+10 = 28. 
Sum of digit = 2 + 8 = 10

If x = 27, X+10 = 37. 
Sum of digit = 3 + 7 = 10

If x = 90, X + 10 = 100
Sum of digit = 1 + 0 + 0 = 1

Answer is E

drkarish22 · Answer

Why cant we suppose a negative number. 
Lets say,

-54
Sum of digits is 9
now after adding 10 ( -54+10= -44) and 4+4= 8

rajkoushik17 · Answer

can't we assume a negative integer like -54 in that case even 8 is possible. But is not mentioned in the OA.

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