A box in a supply room contains 17 compact of which 5 are rated 13 watt, 8 are r
ID: 3207413 • Letter: A
Question
A box in a supply room contains 17 compact of which 5 are rated 13 watt, 8 are rated 18 watt, and 4 are rated 23 watt. Suppose that three of these bulbs are randomly selected Round your answers to three decimal place. What is the probability that exactly two of the selected bulbs are rated 23 watt? 100 What is the probability that all three of the bulbs have the same rating? What is the probability that one bulb of each type is selected? If bulb are selected one by one unit 23 watt bulb is obtained, what is the probability that it is necessary to examine at least 6 bulbs?Explanation / Answer
13W - 5
18W - 8
23W - 4
(a) what is the probbaility that exactly two of the selected bulbs are rated 23 walt?
Ans:(4C2)*13/(17C3)
=6*13/680
=78/680
=0.1147
the probbaility that exactly two of the selected bulbs are rated 23 walt is 0.1147
(b) What is the probbaility that all three of the bulbs have the same rating?
Ans:(5C3)(8C3)(4C3)/(17C3)
=10*56*4/680
=3.2941
the probbaility that all three of the bulbs have the same rating is 3.2941
(c) What is the probabilty that one bulb of each type is selected?
Ans:5*8*4/(17C3)
=160/680
=0.2352
the probabilty that one bulb of each type is selected is 0.2352
(d) If the bulbs are selected one by one until a 23 -watt bulb is obtained ,what is the probbaility that it is necessary to examine atleast 6 bulbs?
Ans:(13C5)/(17C5)
=1287/6188
=0.2079
the probbaility that it is necessary to examine atleast 6 bulbs is 0.2079
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