If the ten’s digit of a positive two-digit number N is 1 less than the unit’s digit, what number is N?
(1) The sum of the two digits of N is 9.
(2) N is divisible by 5.
The two-digit numbers in which the ten’s digit is one less than the unit’s digit are 12, 23, 34, 45, 56, 67, 78 and 89.
If the Statement (1) alone is given, the only possible number among these is 45. So, we can say that N is 45.
So, Statement (1) alone is sufficient to answer the question uniquely.
Before we conclude (A) as the answer, let us see other statement.
If Statement (2) alone is given, the only possible number among the choices is 45.
So, by the statement (2) alone we can find out the answer.
So, either of these statements is enough to answer the question.
So, the answer is (D).
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