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The largest integer k so that that 3335^k is a divisor of 3336! 2019-10-29
From Brandon:
Hello my name is Brandon and I having difficulties in solving the following question: Given the number 3336! = . What's the greater positive integer number k with the condition that 3335expk is a divisor of 3336!
Thanks for your help.

Answered by Penny Nom.
Factorials 2017-07-27
From dinesh:
Is there any shortcut formula for multiply series numbers. like
1x2x3x4x5.......x100 =?

Answered by Penny Nom.
An exercise with factorials 2016-02-07
From vidhi:
find the value of n: (1-1/2) (2-2/3) (3-3/4)...(15-15/16) = n!/16
Answered by Penny Nom.
Factorials 2014-06-06
From penny:
What is factorial? For eg. Like 2!, 3! 4! Etc.
Answered by Penny Nom.
(1-1/2)(2-2/3)(3-3/4)...(15-15/16)=n!/16 2011-02-15
From Fiona:
Could you help me find the value of n: (1-1/2)(2-2/3)(3-3/4)...(15-15/16)=n!/16
Answered by Penny Nom.
Factorials 2010-03-23
From Leah:
When should you use factorials?
Answered by Robert Dawson.
The tens digit of 0! + 1! + 2! + 3! + ... + 2000! 2009-12-21
From Alicia:
What is the tens digit of 0! + 1! + 2! + 3! + ... + 2000!?
Answered by Robert Dawson and Penny Nom.
The last non cero digit of a factorial 2009-06-12
From Wilson:
How can I find the last non cero digit from a factorial calculation of a big number. For example 10! = 3628800, the last non cero digit is 8. What is the last non cero digit of 10! ??
Answered by Robert Dawson.
The sequence 2n! - 1 2009-02-01
From Penny:
I am trying to help my son with this problem. Find the first five terms of the sequence that can be written from the formula A= 2n !-1.
Answered by Penny Nom.
The tens digit of 0! + 1! + 2! + 3! + 4! .............+9999! + 10000! 2009-01-23
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 n-1 choose r plus n-1 choose r - 1 2008-07-14
From fae:
Prove that

( n ) = ( n – 1) + ( n - 1 )
( r )         ( r )        (r-1)

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.
Sum of factorials 2008-01-26
From Emily:
What is the tens digit in the sum 7! + 8! + 9! ... + 2006!
Answered by Stephen La Rocque.
Finding the last non-zero digits of large factorials 2007-10-04
From Mukesh:
i have to find last five non zero digits of integer which can be very large ( upto 10^12) . i can find last non zero digit of of any factorial. Now my problem is that i have to find last five non zero digit of factorial and also i want to general method for last K non zero digits of factorial n. For example 10!=3628800 so last non zero digit is 8 ,last two non zero digit is 88 .....and last five non zero digit is 36288.
Answered by Victoria West.
Factorial fraction 2007-08-03
From Sekhoane:
Expand completely: (N-2)!/N!(9N-1)!
Answered by Stephen La Rocque.
Combinations 2007-05-09
From Michael:
Show that 5 X C(n,5) = n X C(n-1,4)
Answered by Stephen La Rocque.
Probability of getting an A 2007-05-09
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.
n-1/(n+1)! + n+1/n! 2007-03-18
From Cody:
How do you go about simplifying something like this; n-1/(n+1)! + n+1/n!?
Answered by Steve La Rocque and Claude Tardif.
How to find the odds for a lottery jackpot 2006-04-12
From Harvey:
Is it best to use factorials to calculate the odds of winning a lottery, such as the MegaMillions that is popular in the US, or is there a better way?
Answered by Stephen La Rocque.
Prove that p^n >= (p!)/(p-n)! 2006-02-02
From Rhydian:


pn >= (p!)/(p-n)!

Answered by Penny Nom.
Four people are in a race 2006-01-26
From Tammy:
If 4 people are in a race, how many different placements, i.e., 1st, 2nd, 3rd, 4th, can there be and what is the equation?
Answered by Penny Nom.
112! 2004-05-28
From Beatriz:
1) A bus driver collects identical sets of 5 coins from each passenger. If the totoal colledted was $21.83, how many pennies did the driver get??

2) How many terminal zero in the base 10 expression of 112! (factional) N! means N(N-1)(N-2) .....(2) (1).

Answered by Penny Nom.
n! > n^2 2004-03-30
From Jose:
How can you prove by mathematical induction that:

n! > n2.

Answered by Penny Nom.
When is 1! + 2! + 3! + ... + x! a square? 2002-08-19
From Sarathy:
Solve :

1! + 2! + 3! + ... + x! = y 2

How do i find the solutions ?

Answered by Claude tardif.
Why is 0! = 1? 2001-01-30
From Diane:
Every math book always claims that 1!=1 and 0!=1 are givens, and that we should just memorize it. i understand the 1! part, but where is the basis for claiming that 0!=1????
Answered by Walter Whiteley.
Four crayons 2001-01-10
From Neyra Espinoza:
You have four crayons (red, blue, yellow, green). If you line them up, how many different combinations can you get?
Answered by Patrick Maidorn.
n! = 42(n-2)! 2000-07-21
From Damon Bailey:
Solve n! = 42(n-2)!
Answered by Paul Betts.
10,000! 2000-07-21
From Lauren:
Hi I was just wondering if you could tell me how many zeros are in 100,000! (factorial.)
Answered by Denis Hanson.
Six digit numbers using 1,2,5,6,7, and 9 2000-03-20
From Rachel:
How many different six-digit numbers can you make using the digits 1,2,5,6,7, and 9? How many of these six digit numbers are divisible by six?
Answered by Claude Tardif and Denis Hanson.
0! + 1! + 2! + 3! + ... + 2000! 1999-10-21
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.
0! 1997-03-02
From Donna D. Hall:
I am looking for a quick and easy explanation as to why 0! is 1.
Answered by Walter Whiteley and Denis Hanson.
Divisibility of 2n choose n. 1996-09-24
From Kathy Doan:
Can you prove that "2n choose n" is not divisible by 3, 5, and 7 for infinitely many n?
Answered by Penny Nom.



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