30. Exercise problem XVII

(i) A lot of \(20\) bulbs contain \(4\) defective ones. One bulb is drawn at random from the lot. What is the probability that this bulb is defective?

 

The probability that the drawn bulb is defective \(=\) $\frac{i}{i}$

 

 

(ii) Suppose the bulb drawn in (i) is not defective and is not replaced. Now one bulb is drawn at random from the rest. What is the probability that this bulb is not defective ?

 

The probability that second drawn bulb is not defective when the first drawn is not defective and is not replaced \(=\) $\frac{i}{i}$

 

[Note: Enter the fractions in simplified form.]