







An exercise with factorials 
20160207 

From vidhi: find the value of n: (11/2) (22/3) (33/4)...(1515/16) = n!/16 Answered by Penny Nom. 





Factorials 
20140606 

From penny: What is factorial? For eg. Like 2!, 3! 4! Etc. Answered by Penny Nom. 





(11/2)(22/3)(33/4)...(1515/16)=n!/16 
20110215 

From Fiona: Could you help me find the value of n: (11/2)(22/3)(33/4)...(1515/16)=n!/16 Answered by Penny Nom. 





Factorials 
20100323 

From Leah: When should you use factorials? Answered by Robert Dawson. 





The tens digit of 0! + 1! + 2! + 3! + ... + 2000! 
20091221 

From Alicia: What is the tens digit of 0! + 1! + 2! + 3! + ... + 2000!? Answered by Robert Dawson and Penny Nom. 





The tens digit of 0! + 1! + 2! + 3! + 4! .............+9999! + 10000! 
20090123 

From Kaylyn: determine the tens digit for the expression:
0! + 1! + 2! + 3! + 4! .............+9999! + 10000! Answered by Robert Dawson and Penny Nom. 





n choose r equals n1 choose r plus n1 choose r  1 
20080714 

From fae: Prove that
( n ) = ( n – 1) + ( n  1 )
( r ) ( r ) (r1)
NOTE: the ( ) should be one for n taken r and so on. but there is no one big ( ) that will cater two lines Answered by Janice Cotcher. 





Factorial fraction 
20070803 

From Sekhoane: Expand completely: (N2)!/N!(9N1)! Answered by Stephen La Rocque. 





Probability of getting an A 
20070509 

From Christine: In a class of 15 people, exactly 3 got an A. If 2
people are randomly chosen from this class, what is the probability that
at least one of these 2 got an A? Answered by Paul Betts. 





n1/(n+1)! + n+1/n! 
20070318 

From Cody: How do you go about simplifying something like this;
n1/(n+1)! + n+1/n!? Answered by Steve La Rocque and Claude Tardif. 





Prove that p^n >= (p!)/(pn)! 
20060202 

From Rhydian:
PROVE:
p^{n} >= (p!)/(pn)!
Answered by Penny Nom. 





n! > n^2 
20040330 

From Jose: How can you prove by mathematical induction that:
n! > n2. Answered by Penny Nom. 





When is 1! + 2! + 3! + ... + x! a square? 
20020819 

From Sarathy: Solve : 1! + 2! + 3! + ... + x! = y^{ 2} How do i find the solutions ? Answered by Claude tardif. 





10,000! 
20000721 

From Lauren: Hi I was just wondering if you could tell me how many zeros are in 100,000! (factorial.) Answered by Denis Hanson. 





0! + 1! + 2! + 3! + ... + 2000! 
19991021 

From Melissa: My name is melissa. I am a 9th grade student I am having trouble finding out how to do this: What is the tens digit of 0! + 1! + 2! + 3! + ... + 2000! I know how to find these, but my calculator cant go any higher than 69! Is there any way i can do this problem? Answered by Penny Nom. 

