Advertisements
Advertisements
Question
Evaluate `("n"!)/("r"!("n" - "r")!)` when for any n with r = 2
Advertisements
Solution
For any n with r = 2
`("n"!)/("r"!("n" - "r")!)= ("n"!)/(2!("n" - 2)!)`
= `("n"("n" - 1)("n" - 2)!)/(1 xx 2 xx ("n" - 2)1)`
= `("n"("n" - 1))/2`
= `("n"^2 - "n")/2`
APPEARS IN
RELATED QUESTIONS
How many two letter words can be formed using letters from the word SPACE, when repetition of letters is allowed?
How many numbers between 100 and 1000 have 4 in the units place?
How many three-digit numbers can be formed from the digits 0, 1, 3, 5, 6 if repetitions of digits are allowed?
How many three-digit numbers can be formed using the digits 2, 3, 4, 5, 6 if digits can be repeated?
Answer the following:
A hall has 12 lamps and every lamp can be switched on independently. Find the number of ways of illuminating the hall.
How many two-digit numbers can be formed using 1, 2, 3, 4, 5 without repetition of digits?
To travel from a place A to place B, there are two different bus routes B1, B2, two different train routes T1, T2 and one air route A1. From place B to place C there is one bus route say B1, two different train routes say T1, T2 and one air route A1. Find the number of routes of commuting from place A to place C via place B without using similar mode of transportation
Find the number of ways of distributing 12 distinct prizes to 10 students?
Find the value of 6!
Find the value of 3! – 2!
Find the value of 3! × 2!
Evaluate `("n"!)/("r"!("n" - "r")!)` when n = 10, r = 3
Choose the correct alternative:
The number of five digit telephone numbers having at least one of their digits repeated i
Choose the correct alternative:
The number of 10 digit number that can be written by using the digits 2 and 3 is
In a class, there are 27 boys and 14 girls. The teacher wants to select 1 boy and 1 girl to represent the class for a function. In how many ways can the teacher make this selection?
How many numbers are there between 99 and 1000 having 7 in the units place?
In an examination there are three multiple choice questions and each question has 4 choices. Number of ways in which a student can fail to get all answer correct is ______.
If the letters of the word RACHIT are arranged in all possible ways as listed in dictionary. Then what is the rank of the word RACHIT?
There will be only 24 selections containing at least one red ball out of a bag containing 4 red and 5 black balls. It is being given that the balls of the same colour are identical.
If the number of five-digit numbers with distinct digits and 2 at the 10th place is 336 k, then k is equal to ______.
