The following table gives the life time of 400 neon lamps:

Question:

The following table gives the life time of 400 neon lamps:

A bulb is selected at random. Find the probability that the lifetime of a selected bulb:

1. Less than 400 hrs

2. between 300 - 800 hours

3. At least 700 hours

Solution:

Total number of bulbs = 400

1. Probability that the life of the selected bulb is less than 400 hrs

$=\frac{\text { No of bulbs having life less than } 400 \mathrm{hrs}}{\text { Total no of bulbs }}$

= 14/400 

= 7/200

2. Probability that the life of the selected bulb is between 300 - 800 hrs

$=\frac{\text { No of bulbs having life less than } 400 \mathrm{hrs}}{\text { Total no of bulbs }}$

$=\frac{14+56+60+86+74}{200}$

= 290/400 

= 29/40

3. Probability that the life of the selected bulb is at least 700 hrs

$=\frac{\text { No of bulbs having life at least } 700 \mathrm{hrs}}{\text { Total no of bulbs }}$

$=\frac{74+62+48}{400}$

= 184/400 

= 23/50

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