Question

Bulbs are packed in cartons each containing 40 bulbs. Seven hundred cartons were examined for defective bulbs and the results are given in the following table:

No. of defective bulbs	0	1	2	3	4	5	6	more than 6
frequency	400	180	48	41	18	8	3	2

One carton was selected at random. The probability of defective bulbs being less than 4 is

• A. $\frac{89}{700}$
• B. $\frac{432}{700}$
• C. $\frac{600}{700}$
• D. $\frac{669}{700}$

Answer 1

The correct option is D $\frac{669}{700}$

$P\left(\text{carton having defective bulbs less than 4}\right)$

$=1-P\left(\text{carton having defective bulbs greater than or equal to 4}\right)$

$=1-\frac{18+8+3+2}{700}=1-\frac{31}{700}=\frac{669}{700}$