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#

Related questions
See all questions in Factorial Identities
Impact of this question
2041 views around the world
You can reuse this answer
Creative Commons License