A child is told she can bring five toys with her on holiday. the child decides to choose the five from
6 jigsaws, 8 dolls, 4 balls, 2 trucks.
How many of these sets have at least one from each of the four categories of toy listed above?
6 jigsaws, 8 dolls, 4 balls, 2 trucks.
How many of these sets have at least one from each of the four categories of toy listed above?
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The possibilities are JJDBT or JDDBT or JDBBT or JDBTT
Number of ways of selecting r number of items out n is given by nCr = n!/(r!*(n-r)!)
Total number of ways of selecting 5 toys = 6C2*8C1*4C1*2C1 + 6C1*8C2*4C1*2C1 + 6C1*8C1* 4C2*2C1 + 6C1*8C1*4C1*2C2
= 15*8*4*2 + 6*28*4*2 + 6*8*6*2 + 6*8*4*1
= 960 + 1344 + 576 + 192
= 3072
Number of ways of selecting r number of items out n is given by nCr = n!/(r!*(n-r)!)
Total number of ways of selecting 5 toys = 6C2*8C1*4C1*2C1 + 6C1*8C2*4C1*2C1 + 6C1*8C1* 4C2*2C1 + 6C1*8C1*4C1*2C2
= 15*8*4*2 + 6*28*4*2 + 6*8*6*2 + 6*8*4*1
= 960 + 1344 + 576 + 192
= 3072
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6 choices for jigsaws times
8 choices for dolls time
4 choices for balls times
2 choices for trucks.
that's 96•4 = 384 choices for 1 of each, which leaves 16 choices for the 5th toy, and
384 • 16 = 6144
which is twice your "answer"
8 choices for dolls time
4 choices for balls times
2 choices for trucks.
that's 96•4 = 384 choices for 1 of each, which leaves 16 choices for the 5th toy, and
384 • 16 = 6144
which is twice your "answer"