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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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