Question

A die is thrown once. Probability of getting a number other than 3 is :

• A. $\frac{1}{6}$
• B. $\frac{3}{6}$
• C. $\frac{5}{6}$
• D. 1

Hint:

Using the complement rule ($1 - P(A)$) is extremely efficient for "other than" or "at least" questions in probability.
It simplifies counting when the number of favorable outcomes is large.

Answer 1

The Correct Option is C

Step 1: Use the complement rule instead of counting directly.
"Not getting a 3" is the complement of "getting a 3", so $P(\text{not }3)=1-P(3)$.
Step 2: Find the probability of the simpler event.
There's only one favourable outcome (rolling a 3) out of 6 equally likely faces, so $P(3)=\frac16$.
Step 3: Subtract from 1.
$P(\text{not }3)=1-\frac16=\frac56$.
\[ \boxed{\dfrac{5}{6}} \]