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Probability and permutations

CONCEPTS

Probability an event will occur from multiple selections

• Probability = Total number of permutations where the scenario WILL occur / Total number of permutations


Tips

• Count the values for the numerator and denominator or use the equation to solve the problem.

PRACTICE PROBLEMS

Question 1 There are 45 kids in Grade 2 and 20 kids in Grade 5 at a school. Suppose 2 kids will be selected. What’s the probability they will be from the same grade?


-- Answer -- (45)(44) / 65*64 + (20)(19) / 65*64

Probability = (45)(44) / 65*64 + (20)(19) / 65*64

ACT PRACTICE PROBLEMS

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