Question

Out of $400$ bulbs in a box, $15$ bulbs are defective. One bulb is taken out at random from the box. Find the probability that the drawn bulb is not defective.

• A. True
• B. False

Answer 1

Step 1: Find the number of non-defective bulbs in the box:

Given that, the total number of bulbs in a box will be $400$.

The total number of defective bulbs are $15$.

Therefore, the total number of non-defective bulbs in the box is:
$$\begin{gathered} =400-15 \\ =385 \end{gathered}$$

Step 2: Use the formula for probability:

$\text{Probability =}\frac{\text{Number of non defective bulbs in the box}}{\text{Total number of bulbs in the box}}$

Thus, the probability will be,

$$\begin{gathered} \text{Probability=}\frac{385}{400} \\ \mathrm{Probability}\text{=}\frac{77}{80} \end{gathered}$$

Final answer:

Hence, the probability that the drawn bulb is not defective is $\frac{77}{80}$.