Question

There are $500$ packets in a large box and each packet contains $4$ electronic devices in it. On testing, at the time of packing, it was noted that there are some faulty pieces in the packets. The data is as below :

No. of faulty devices in a packet	Number of packets
$0$	$300$
$1$	$100$
$2$	$50$
$3$	$30$
$4$	$20$
Total number of packets	$500$

If one packet is drawn from the box, what is the probability that all the four devices in the packet are without any fault?

• A. $0.5$
  
• B. $0.6$
• C. $0.8$
• D. $0.9$

Answer 1

The correct option is B $0.6$

When the packet has all the four devices without fault, it means the number of faulty devices in the packet is $0$. Number of chances which are favourable to $0$ are $300$ as given in the table above.
Thus, the probability of packet containing all the four devices without any fault $=$ $\frac{300}{500}$ $=$ $\frac{3}{5}$ $=0.6$