Discussion :: Problems on Numbers

What is the twodigit number?
I. The difference between the two digits is 9.
II. The sum of the digits is equal to the difference between the two digits.
A.
I alone sufficient while II alone not sufficient to answer 
B.
II alone sufficient while I alone not sufficient to answer 
C.
Either I or II alone sufficient to answer 
D.
Both I and II are not sufficient to answer 
E.
Both I and II are necessary to answer 
Answer : Option E
Explanation :
Let the tens and unit digits be x and y respectively. Then,
I. x  y = 9.
II. x + y = x  y.
From I and II, we get x  y = 9 and x + y = 9.
On solving, we get x = 9 and y = 0.
Required number is 90.
Thus, both I and II are needed to get the answer.
Correct answer is (E).
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