Why his formula doesn't work on my calculator?

[Ero]

Why this formula doesn't work on my calculator?

94!
______

2! * 92!

it says math error

 

[Deleted member 4993]

94!
______

2! * 92!

it says math error

I am looking at a TI-84 and I cannot find factorial operation.

What type of calculator do you have?

94! is a very large number - probably it has overflow problem.

One way to get arond the problem is to realize that 94!/92! = 94*93

 

[Ero]

I am looking at a TI-84 and I cannot find factorial operation.

What type of calculator do you have?

94! is a very large number - probably it has overflow problem.

One way to get arond the problem is to realize that 94!/92! = 94*93

I know it is a large number but is divides it again

I have fx 82es plus

i don't get the last part of your message

 

[pka]

94!
______
2! * 92!

Have a look at this.

 

[JeffM]

I know it is a large number but is divides it again

I have fx 82es plus

i don't get the last part of your message

What Subhotosh Khan is saying is that we are not experts in brands of calculators, but a plausible explanation is that your calculator cannot compute a number as big as 94!. It has to calculate it before it can divide it.

He is also saying that there is an easy workaround because

\(\displaystyle \dfrac{94!}{92! * 2!} = \dfrac{94 * 93 *92!}{92! * 2!} = \dfrac{94 * 93}{2} = 4371.\) I doubt your calculator will have trouble with 94 * 93 / 2.

 

[Ero]

What Subhotosh Khan is saying is that we are not experts in brands of calculators, but a plausible explanation is that your calculator cannot compute a number as big as 94!. It has to calculate it before it can divide it.

He is also saying that there is an easy workaround because

\(\displaystyle \dfrac{94!}{92! * 2!} = \dfrac{94 * 93 *92!}{92! * 2!} = \dfrac{94 * 93}{2} = 4371.\) I doubt your calculator will have trouble with 94 * 93 / 2.

Thanks for the explanation. So instead of 92! In the nominator I use 94 x 93 x 92! and then simplify it since it is still a big number. But I have a question. Why does the ! Fall away after the simplification?

 

[JeffM]

Thanks for the explanation. So instead of 92! In the nominator I use 94 x 93 x 92! and then simplify it since it is still a big number. But I have a question. Why does the ! Fall away after the simplification?

\(\displaystyle 94! = 94 * 93 * 92!\) Do you understand that?

\(\displaystyle So\ \dfrac{94!}{92! * 2!} = \dfrac{94 * 93 * 92!}{92! * 2!}\) follows immediately.

But I have 92! in the numerator and denominator so they cancel and disappear.

\(\displaystyle \dfrac{94 * 93 * 92!}{92! * 2!} = \dfrac{94 * 93}{2!}.\)

And 2! = 2 * 1 = 2.

\(\displaystyle So\ \dfrac{94 * 93}{2!} = \dfrac{94 * 93}{2},\) which a calculator can handle easily.

 

[Ero]

\(\displaystyle 94! = 94 * 93 * 92!\) Do you understand that?

\(\displaystyle So\ \dfrac{94!}{92! * 2!} = \dfrac{94 * 93 * 92!}{92! * 2!}\) follows immediately.

But I have 92! in the numerator and denominator so they cancel and disappear.

\(\displaystyle \dfrac{94 * 93 * 92!}{92! * 2!} = \dfrac{94 * 93}{2!}.\)

And 2! = 2 * 1 = 2.

\(\displaystyle So\ \dfrac{94 * 93}{2!} = \dfrac{94 * 93}{2},\) which a calculator can handle easily.

I understand it now. Thanks a bunch.

last question. What are these ! Operations called?

 

[pka]

last question. What are these ! Operations called?

That is called the factotial operator. It is in general only applied to natural numbers.

Defined as
\(\displaystyle 0!=1\\1!=1\\2!=(1)(2)\\3!=(1)(2)(3)\\\vdots\\N!=(N)(N-1)(N-2)\cdots(2)(1) \)

Now that means \(\displaystyle N!=(N)(N-1)! \)

 

[JeffM]

I understand it now. Thanks a bunch.

last question. What are these ! Operations called?

n! is called n factorial, and it comes up in combinatorics and probability theory.

A slightly different definition from the previous one is:

n = 0, then n! = 1; and

n is a natural number > 0, then n! = n * (n - 1)!.

The two definitions amount to the same thing.