Mairisa gets $8 per week for an allowance. She saves 25% of her allowance each week. How long will it take Mauritania to save $1
2 answers:
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Remark
Many calculators have a key that will do this in one step. Mine is one of them. So let's start with the answer and then we'll do it the long way.
9C3 = 84. You put it into your calculator as 9 2nF nCr 3 =
Solution
3*4*7 = 84 which is what you set out to show.