Mary purchased a package of 15 different plants, but she only needed 10 plants for planting. In how many ways can she select the 10 plants from the package to be planted?
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Solution: Number of ways to plant 10 out of 15 =15C10= 15C5 =(15x14x13x12x11)/(1x2x3x4x5)
= 360360/120 = 3003..........Ans
= 360360/120 = 3003..........Ans
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it's a permutation question.
permutation is were you times down from that number.
so
if the question was how many ways can mary chose the order of 15 plants the calculations would go:
15 x 14 x 13 x 12 x 11 x 10 x 9 x 8 x 7 x 6 x 5 x 4 x 3 x 2 x 1 =
because mary only needs 10 plants we stop after multiplying the upper 10 figures.
15 x 14 x 13 x 12 x 11 x 10 x 9 x 8 x 7 x 6 =
pretty simple. i think you can do the sums and work out the answer yourself.
permutation is were you times down from that number.
so
if the question was how many ways can mary chose the order of 15 plants the calculations would go:
15 x 14 x 13 x 12 x 11 x 10 x 9 x 8 x 7 x 6 x 5 x 4 x 3 x 2 x 1 =
because mary only needs 10 plants we stop after multiplying the upper 10 figures.
15 x 14 x 13 x 12 x 11 x 10 x 9 x 8 x 7 x 6 =
pretty simple. i think you can do the sums and work out the answer yourself.
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15C10 = 3003