A certain type of flashlight requires two type-D batteries, and the flashlight w

Question

A certain type of flashlight requires two type-D batteries, and the flashlight will work only if both its batteries have acceptable voltages. Suppose that 80% of all batteries from a certain supplier have acceptable voltages. Among twenty randomly selected flashlights, what is the probability that at least nineteen will work? (Round your answer to three decimal places.) What assumptions did you make in the course of answering the question posed? we have assumed here that the batteries' voltage levels are independent. We have assumed here that the batteries' voltage levels are dependent. You may need to use the appropriate table in the Appendix of Tables to answer this question.

Explanation / Answer

for atleast 19 to be working we need o calculate the probability of 19 working or all 20 working.

probability of a battery working = 80% = 0.8

probability of battery not working = 1 - 0.8 =0.2

probability of all 20 working = 0.820

probability of 19 working and 1 not working = 0.819 *0.2

hence total probability = 0.820 + 0.819 *0.2

= 0.01153 + 0.0029

= 0.01443

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