Each time the student will pick 6 books, 2 of each type. I'll write out all possible selections for the "lit" books (4 to choose from):
1,2
1,3
1,4
2,3
2,4
3,4
Total of 6 possible combinations.
The formula for figuring out the number of possible combinations is:
x * (x-1) / 2
4 * (4-1) / 2 = 6
For the other types of books, the formula works out like this:
math = 6 books = 15 combinations
science = 8 books = 28 combinations
Now it's simple to calculate the rest since we're grabbing the books from different categories, we just multiply the number of combinations to get the total number of possibilities.
Total = 6 * 15 * 28 = 2520
2006-07-08 19:06:34
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answer #1
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answered by tom_2727 5
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for the math books, you calculate how many combinations there are of 2 books taken from a group of 6. The answer is 15. To calculate that, it's 6!/2!(6-2)! = 6!/(2!x4!) = 6x5x4x3x2x1/2x1x4x3x2x1 = 30/2 = 15.
Use the same formula for the 8 science books 8!/2!(6!) = 56/2 - 28
For the lit books, is 4!/(2!x 2!) = 6
So if there are 15 possible combinations of math books, 28 combinations of science books, and 6 combinations of lit books, there are 15 x 28 x 6 ways to select two of each book, or 2520 ways to select two of each.
2006-07-08 18:57:44
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answer #2
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answered by Judy 7
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6*2=12
8*2=16
4*2=8
16*12*8=1536
1536 ways to choose those books.
2006-07-08 18:36:16
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answer #3
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answered by Anonymous
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6choose2 * 8choose2 * 4choose2
=[(6!) / (4!*2!) ] * [(8!) / (6!*2!)] * [(4!) / (2!*2!)]
=[(6*5*4*3*2*1)/(4*3*2*1 * 2*1)] *
[(8*7*6*5*4*3*2*1)/(6*5*4*3*2*1 * 2*1)] *
[(4*3*2*1) / (2*1 * 2*1)]
=[(6*5)/(2*1)] * [(8*7)/(2*1)] * [(4*3)/(2*1)]
=15 * 28 * 6 = 2520
2006-07-09 09:30:28
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answer #4
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answered by Anonymous
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i think you multiply all of the numbers, i'm pretty sure you do it that way
2006-07-08 18:35:28
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answer #5
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answered by smile 2
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