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i can't answer
Date Posted: 4 years ago
Views: 427
first, work out no. of ways to buy all the different possible combinations of 10 plants ...,
indoor + outdoor ...
10 + 0 -> 0 ways
9 + 1 -> 9C9 x 12C1 = 12 ways
8 + 2 -> 9C8 x 12C2 = 594 ways
7 + 3 -> 9C7 x 12C3 = 7920 ways
6 + 4 -> 9C6 x 12C4 = 41580 ways
5 + 5 -> 9C5 x 12C5 = 99792 ways
4 + 6 -> 9C4 x 12C6 = 116424 ways
3 + 7 -> 9C3 x 12C7 = 66528 ways
2 + 8 -> 9C2 x 12C8 = 17820 ways
1 + 9 -> 9C1 x 12C9 = 1980 ways
0 + 10 -> 9C0 x 12C10 = 66 ways
total ways = 12 + 594 + 7920 + ... + 66
= 352716
(a) P(buys 3 + 7) = 66528 / 352716 = 792 / 4199
(b) P(at least 7 indoor)
= P(buys 9+1) + P(buys 8+2) + P(buys 7+3)
= (12+594+7920) / 352716
= 203 / 8398
this should be right method, but please recheck all calculations in case I have made calculation error.
indoor + outdoor ...
10 + 0 -> 0 ways
9 + 1 -> 9C9 x 12C1 = 12 ways
8 + 2 -> 9C8 x 12C2 = 594 ways
7 + 3 -> 9C7 x 12C3 = 7920 ways
6 + 4 -> 9C6 x 12C4 = 41580 ways
5 + 5 -> 9C5 x 12C5 = 99792 ways
4 + 6 -> 9C4 x 12C6 = 116424 ways
3 + 7 -> 9C3 x 12C7 = 66528 ways
2 + 8 -> 9C2 x 12C8 = 17820 ways
1 + 9 -> 9C1 x 12C9 = 1980 ways
0 + 10 -> 9C0 x 12C10 = 66 ways
total ways = 12 + 594 + 7920 + ... + 66
= 352716
(a) P(buys 3 + 7) = 66528 / 352716 = 792 / 4199
(b) P(at least 7 indoor)
= P(buys 9+1) + P(buys 8+2) + P(buys 7+3)
= (12+594+7920) / 352716
= 203 / 8398
this should be right method, but please recheck all calculations in case I have made calculation error.
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Date Posted:
4 years ago
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