Factorials - Find x if 1/4! + 1/5! = x/6!

Question:

Find 'x' if 1/4! + 1/5! = x/6!


Solution:

x/6! = 1/4! + 1/5!

∴ x/6! = (6 x 5) / [(6 x 5) x 4!] + 6 / 6 x 5!

∴ x/6! = 30 / 6! + 6 / 6!

∴ x/6! = (30 + 6) / 6!

∴ x/6! = 36 / 6!

∴ x/ ̶6̶!̶ = 36 / ̶6̶!̶

∴ x = 36


Answer:

x = 36 if 1/4! + 1/5! = x/6!


Video Solution:



Find 'x' if 1/4! + 1/5! = x/6! A solved example on Factorial in Permutations and Combinations