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Marty has exactly 5 blue pens, 6 black pens, and 4 red pens in his knapsack. If he pulls out one pen at random from his knapsack, what is the probability that the pen is either red or black?

11/15
2/3
1/2
1/3
1/5

2007-10-09 17:55:04 · 4 answers · asked by Anonymous in Science & Mathematics Mathematics

4 answers

Somebody already answered with the right answer, 2/3... BUT if you want to know how it's solved....

You add up the total number of pens (15), and that becomes your denominator of the fraction. Your numerator is the number of pens possible that are red or black (10). So, your answer is 10/15. Then, you need to reduce the fraction-both numbers are divisible by 5, so you get 2/3.

Good luck and have fun!

2007-10-09 18:05:03 · answer #1 · answered by Anonymous · 2 0

2/3

2007-10-09 17:58:30 · answer #2 · answered by Anonymous · 1 0

upload all of the pens first: 3+4+5 = 12 so there are 12 pens all in all. ask your self, "what proportion black pens are there?" the respond is 5 black pens considering there are 5 black pens, the prospect of taking a black pen = 5 black pens / 12 pens 5/12 ---> threat of taking a black pen threat of no longer having a black pen = 12/12 - 5/12 = 7/12 7/12 ---> threat of taking a non-black pen

2016-12-18 03:28:27 · answer #3 · answered by ? 4 · 0 1

P(red) = 4/15
P(black) = 6/15
P(red or black)
= 4 / 15 + 6 / 15
= 10 / 15
= 2 / 3

2007-10-09 20:02:42 · answer #4 · answered by Como 7 · 2 0

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