Question

By accident, 6 burned out bulbs have additionally been mixed in with 28 good ones. Ken is replacing old bulbs in his house. If he selects two bulbs at random from the box of 34, what is the probability they both work?

P(Both Work) = 196 / 289

P(Both Work) = 5 / 187

P(Both Work) = 325 / 512

P(Both Work) = 126 / 187

Answer 1

P(Both work) = 126/187

Explanation:

Number of burned out bulbs = 6

Number of good ones = 28

Therefore;

P( Not working bulb) = 6/34

P (working bulb) = 28/34

Therefore;

Probability of choosing a working bulb the first time = 28/34

Probability of choosing a working bulb the second time = 27/33

Hence;

P(Both work) = 28/34 × 27/33

= 126/187