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 9.
II. Its tens digit is twice its units 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 (\(t+u=9\)):
18, 27, 36, 45, 54, 63, 72, 81 and 90 all fit: not sufficient
Statement II alone (\(t=2u\)):
21, 42, 63 and 84 all fit: not sufficient
Both together:
\(2u+u=9\), so \(u=3\) and \(t=6\)
The number is 63: sufficient together