Anshika Y.

asked • 04/19/21

A problem on probability

Quen: Given a box with 2 25-watt, 3 40-watt, and 4 100-watt bulbs, in how many ways could 3 bulbs be selected from the box?

(A). How many of these selections of three bulbs would include both 25-watt bulbs? How many would include no 25-watt bulbs?

(B). How many bulb selections defined in (A) part would include exactly 1 of each of the 3 different wattages?

Joel L.

tutor
Something is off in the question. There are only 225-watt, 340-watt, and 4100-watt bulbs in a box. So where does 25-watt bulb belong? It didn't say it is in the box. Another thing is 4100-watt bulb consumes a lot of power. I don't think there is such kind of bulb. Perhaps you meant two 25-watt, three 40-watt and four 100-watt bulb. I'm not so sure of the question.
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04/19/21

Anshika Y.

Yes its 25,40 and 100
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04/19/21

1 Expert Answer

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Prakrati A. answered • 04/19/21

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Choosing 3 bulbs out of 9 different watt bulbs. It will be 9C3 = (9 X 8 X 7)/(3X2). = 84 ways.

How many of these will include the 2 25 watt bulbs?

For this you have already selected 2 25 watt bulbs, selecting which is 2C2 = 1

Now you have to select one bulb from 7 bulbs. 7C1 = 7 ways

So if you need to select one from each wattage, it will be: 2C1 X 3C1 X 4C1 = 2 X 3 X 4 = 24 ways

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Anshika Y.

Thanku so much ma'am !
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04/20/21

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