Question

The smallest two-digit triangular number is ___.

• A. 9
• B. 3
• C. 10
• D. 16

Answer 1

The correct option is C 10

It is evident from the options that option A and option C are one digit numbers. So, they can be discarded.

The number is option D, i.e. 16 is a square number. It can be written as the product of two same numbers,
i.e., 4 $\times$ 4 = 16

Now let's look at option B.
10 is a triangular number. It can be represented as:
Hnece, option B is the correct answer.