Question
Wed December 07, 2011 By:

# n(n-1)(n-2).......(n-r+1) how do we get (n-r+1)?explain with an numerical example

Thu December 08, 2011
The given product is n(n-1)(n-2) and so on..
Which can be written as (n-0)(n-1)(n-2) ..and so on..
In the above product,the first term is (n-0).
The second term is (n-1),the third term is (n-2) and so on...
So,if we take the no of the term to be 'r'.
For the first term ,r=1,keeping 'n' as fixed.
We can write the First term=(n-0) as (n-1+1)
Similarly,second term=(n-1) can be written as:
(n-2+1)
Third term=(n-2),can be written as (n-3+1)
Generalising and Proceeding similarly,
we get the rth term as (n-r+1)
Related Questions
Fri September 08, 2017

# Q. Ex. 8.3 - 25(ii) P.No. 441 : How mant different five letter words starting with  a vowel can be formed from the letters of the word EQUATION ? ans. 4200 Q. Ex. 8.3 - 28(Iii) P.No. 441 : How many numbers greater than 20000 can be formed by using the digits 0,1,2,3,4 with no digit being repeated ? ans. 72     Q. Ex. 8.3 - 29,  P.No. 441 : A moped licence plate has two letters and then four number in it . How many plates can be made without duplicating . There are no plates with number zero ? ans. 6759324 Q. Ex. 8.3 - 30, P.No. 441 : In an examination m there are three multiple choise questions and each question has four choices. Find the number of ways in which a student can fail to get all correct answers? ans. 43 Q. Ex. 8.3 - 31, P.No. 441 : There are three prizes to be distributed among six boys. In how many ways can it be done when (i) no boy gets more than one prize. (ii)there is no restriction as to the number of prizes any boy gets , (iii)no boy gets all the prizes ? ans. 120/216/210 Q. Ex. 8.3 - 32, P.No. 441 : There are 3 candidates and 5 voters. In how many ways can the votes be given ? If three candidates are among 5 voters and they vote for themselves only, then how many ways of giving votes are possible ? Why should everyone vote ? ans. 243/9

Fri September 08, 2017