A-Level Maths - Core/Pure 1
A visual explanation of permutation and combination
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Combinations made easy
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Combinations and Permutations
"My fruit salad is a combination of apples, grapes and bananas" We don't care what order the fruits are in, they could also be "bananas, grapes and apples" or "grapes, apples and bananas", its the same fruit salad.
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Permutations And Combinations Exam Questions