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I was wondering about ab! (a and b are integers, ! is factorial). Do we first multiply a and b then factorial the product or do we factorial the b and then multiply.

Note by Djordje Marjanovic
3 years, 10 months ago

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Depends on the problem statement. Usually either \((\overline{ab})!, (ab)!, a\cdot b!\) is given so you don't need to worry. If it is ambigious, ask the composer. But I would treat this as \((ab)!\). Zi Song Yeoh · 3 years, 10 months ago

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if you are referring to (a*b)! then you should multiply them first and then find the factorial. Sudha Parimala · 3 years, 10 months ago

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If the problem states explicitly that ab is a two digit number, you should find the factorial of the two digit number. Like \(a=2,b=1\), calculate 21!. Aditya Parson · 3 years, 10 months ago

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You are necessitated to multiply them first and then evaluate the factorial. Think of \((2*3)!=720\), and \(2*3!=12\). See the difference? Shourya Pandey · 3 years, 10 months ago

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