The question below is followed by two statements numbered I and II. Choose the option that describes whether the statements are sufficient to answer the question.
What is the two-digit number?
I. The sum of its digits is 12.
II. Its units digit is three times its tens digit.
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → The question can be answered by using both statements together, but not by using either statement alone.
Let the tens digit be \(t\) and the units digit be \(u\); the number is \(10t+u\).
Statement I alone (\(t+u=12\)):
39, 48, 57, 66, 75, 84 and 93 all fit: not sufficient
Statement II alone (\(u=3t\)):
13, 26 and 39 all fit: not sufficient
Both together:
\(t+3t=12\), so \(t=3\) and \(u=9\)
The number is 39: sufficient together