Question

A number is selected at random from $1$ to $50$. What is the probability that it is a triangular number

Answer 1

The total number of outcomes are $50$.

Now, if a number is selected at random then the possible outcomes that it is a triangular number are

{$1,3,6,10,15,21,28,36,45$} which means the number of favourable outcome is $9$.

Therefore, probability $P$ that it is a triangular number is:

$P=\frac{9}{50}$

Hence, the probabilitythat it is a triangular number is $\frac{9}{50}$.