SIMPLIFY THE FACTORIAL EXPRESSION

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What is factorial ?

Factorial of a whole number n is defined as the product of that number with every whole number less than or equal to n till 1. 

For all positive integers, n! is defined as

n! = n (nāˆ’1) (nāˆ’2)⋯(2)(1)

4! = 4 x 3 x 2 x 1

4! = 24

How to simplify factorial expression ?

To simplify factorial expression, first we have to choose the larger value and write it in descending order as product of terms.

Simplify without using a calculator.

Problem 1 :

6! / 5!

Solution :

6! / 5! = (6 āˆ™ 5 āˆ™ 4 āˆ™ 3 āˆ™ 2 āˆ™ 1) / (5 āˆ™ 4 āˆ™ 3 āˆ™ 2 āˆ™ 1)

= 6

Alternatively :

6! = (6 āˆ™ 5!) / 5!

= 6

Determine the value for each expression. Simplify fully before using a calculator.

Problem 1 :

8! / 5!

Solution :

8! / 5! = (8 Ɨ 7 Ɨ 6 Ɨ 5!) / 5!

= 8 Ɨ 7 Ɨ 6

8! / 5! = 336

Problem 2 :

19! / 13!

Solution :

19! / 13! = (19 Ɨ 18 Ɨ 17 Ɨ 16 Ɨ 15 Ɨ 14 Ɨ 13!) / 13!

= 19 Ɨ 18 Ɨ 17 Ɨ 16 Ɨ 15 Ɨ 14

19! / 13! = 19535040

Problem 3 :

21! / 17! 4!

Solution :

21! / 17! 4! = (21 Ɨ 20 Ɨ 19 Ɨ 18 Ɨ 17!) / 17! (4 Ɨ 3 Ɨ 2 Ɨ 1)

= (21 Ɨ 20 Ɨ 19 Ɨ 18) / (4 Ɨ 3 Ɨ 2 Ɨ 1)

= 143640 / 24

21! / 17! 4! = 5985

Problem 4 :

9! / 7! 2!

Solution :

9! / 7! 2! = (9 Ɨ 8 Ɨ 7!) / 7! (2 Ɨ 1)

= 72 / 2

9! / 7! 2! = 36

Problem 5 :

155! / 152!

Solution :

155! / 152! = (155 Ɨ 154 Ɨ 153 Ɨ 152!) / 152!

= 155 Ɨ 154 Ɨ 153

155! / 152! = 3652110

Problem 6 :

93! / 89! 4!

Solution :

93! / 89! 4! = (93 Ɨ 92 Ɨ 91 Ɨ 90 Ɨ 89!) / 89! (4 Ɨ 3 Ɨ 2 Ɨ 1)

= (93 Ɨ 92 Ɨ 91 Ɨ 90) / (4 Ɨ 3 Ɨ 2 Ɨ 1)

= 70073640 / 24

93! / 89! 4! = 22919735

Determine the value for each expression. Simplify fully before using a calculator.

Problem 7 :

10! / 5!

Solution :

10! / 5! = (10 Ɨ 9 Ɨ 8 Ɨ 7 Ɨ 6 Ɨ 5!) / 5!

= 10 Ɨ 9 Ɨ 8 Ɨ 7 Ɨ 6

10! / 5! = 30240

Problem 8 :

21! / 14!

Solution :

21! / 14! = (21 Ɨ 20 Ɨ 19 Ɨ 18 Ɨ 17 Ɨ 16 Ɨ 15 Ɨ 14!) / 14!

= 21 Ɨ 20 Ɨ 19 Ɨ 18 Ɨ 17 Ɨ 16 Ɨ 15

21! / 14! = 586051200

Problem 9 :

9! / 3! 6!

Solution :

9! / 3! 6! = (9 Ɨ 8 Ɨ 7 Ɨ 6!) / 6! (3 Ɨ 2 Ɨ 1)

= (9 Ɨ 8 Ɨ 7) / (3 Ɨ 2 Ɨ 1)

= 504 / 6

9! / 3! 6! = 84

Problem 10 :

12! / 8! 4!

Solution :

12! / 8! 4! = (12 Ɨ 11 Ɨ 10 Ɨ 9 Ɨ 8!) / 8! (4 Ɨ 3 Ɨ 2 Ɨ1)

= (12 Ɨ 11 Ɨ 10 Ɨ 9) / (4 Ɨ 3 Ɨ 2 Ɨ1)

= 11880 / 24

12! / 8! 4! = 495

Problem 11 :

7! /2! 5! + 7! / 4! 3!

Solution :

7! /2! 5! + 7! / 4! 3! = (7 Ɨ 6 Ɨ 5!) / 5! (2 Ɨ 1) + (7 Ɨ 6 Ɨ 5 Ɨ 4!) / 4! (3 Ɨ 2 Ɨ 1)

= (42 / 2) + (210 / 6)

= 21 + 35

7! /2! 5! + 7! / 4! 3! = 56

Problem 12 :

(15! / 9! 6!) + (15! / 10! 5!)

Solution :

15! / 9! 6! = (15 Ɨ 14 Ɨ 13 Ɨ 12 Ɨ 11 Ɨ 10 Ɨ 9!) / 9! (6 Ɨ 5 Ɨ 4 Ɨ 3 Ɨ 2 Ɨ1)

= (15 Ɨ 14 Ɨ 13 Ɨ 12 Ɨ 11 Ɨ 10) / (6 Ɨ 5 Ɨ 4 Ɨ 3 Ɨ 2 Ɨ1)

= 3603600 / 720

15! / 9! 6! = 5005

15! / 10! 5! = (15 Ɨ 14 Ɨ 13 Ɨ 12 Ɨ 11 Ɨ 10!) / 10! (5 Ɨ 4 Ɨ 3 Ɨ 2 Ɨ1)

= (15 Ɨ 14 Ɨ 13 Ɨ 12 Ɨ 11) / (5 Ɨ 4 Ɨ 3 Ɨ 2 Ɨ1)

= 360360 / 120

15! / 10! 5! = 3003

15! / 9! 6! + 15! / 10! 5! = 5005 + 3003

15! / 9! 6! + 15! / 10! 5! = 8008

Problem 13 :

2 Ɨ 5! / 2! 3!

Solution :

2 Ɨ 5! / 2! 3! = 2 Ɨ (5 Ɨ 4 Ɨ 3!) / 3! (2 Ɨ 1)

= 2 Ɨ (5 Ɨ 4) / 2

2 Ɨ 5! / 2! 3! = 20

Problem 14 :

3 Ɨ 11! / 7! 4!

Solution :

3 Ɨ 11! / 7! 4! = 3 Ɨ (11 Ɨ 10 Ɨ 9 Ɨ 8 Ɨ 7!) / 7! (4 Ɨ 3 Ɨ 2 Ɨ 1)

= 3 Ɨ (11 Ɨ 10 Ɨ 9 Ɨ 8) / (4 Ɨ 3 Ɨ 2 Ɨ 1)

= 3 Ɨ 330

3 Ɨ 11! / 7! 4! = 990

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