How do you write 30 times 29 using factorials?

1 Answer
mason m
Dec 31, 2015

(30!)/(28!)

Explanation:

The 30xx29xx28...=30! chain is started, but is stopped at everything 28 and under.

(30!)/(28!)=(30xx29xxcolor(red)(cancel(color(black)(28)))xxcolor(red)(cancel(color(black)(27)))xxcolor(red)(cancel(color(black)(26)))xx...xxcolor(red)(cancel(color(black)(3)))xxcolor(red)(cancel(color(black)(2)))xxcolor(red)(cancel(color(black)(1))))/(color(red)(cancel(color(black)(28)))xxcolor(red)(cancel(color(black)(27)))xxcolor(red)(cancel(color(black)(26)))xx...xxcolor(red)(cancel(color(black)(3)))xxcolor(red)(cancel(color(black)(2)))xxcolor(red)(cancel(color(black)(1))))=30xx29

Another way of writing this:

(30!)/(28!)=(30xx29xx28!)/(28!)=30xx29

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