Greetings!

JoshH · 2013-04-25 14:39:51

Greetings everyone my name is Josh I am currently going back to school. It's been a very long time since I did any type of math.
I am looking for some help learning and memorizing how to solve problems. I am currently learning how to use excel
formulas. If anyone can help me please send me a message I'd really appreciate it!

Sincerely,

Josh

bobbym · 2013-04-25 14:43:47

Hi JoshH;

Welcome to the forum. What kind of problems?

mathaholic · 2013-04-25 20:54:54

Hi JoshH!

Welcome.

ShivamS · 2013-04-26 00:17:56

Hello and welcome to the forum.

Bob · 2013-04-26 00:40:22

hi JoshH

Welcome to the forum.

I sometimes use Excel and there are others who can help too.

Bob

JoshH · 2013-04-26 17:33:22

Excel Simulations like figuring out totals over a 12 month period if 3% of the student body drops out of a course each month for twelve months. I figured it out for now but I am sure I will be back the instructions on how to do these problems can be trouble some at times considering I have very experience with math in general.

bobbym · 2013-04-26 17:42:10

That is a problem involving recurrences. It is fairly easy with a programming language, tougher with math. How come you are working on that level of math problem if you say you are inexperienced at math?

JoshH · 2013-04-26 18:25:17

I am currently enrolled in a video game design course. They are teaching me how to do the problems but I am still lost. The course work is online.

bobbym · 2013-04-26 18:29:00

Hi;

Bring them in here when you get them. Recurrences are my specialty. Use programming to check or to get an approximate answer first.

JoshH · 2013-04-26 18:31:19

believe it or not it seams someone already posted the question in a previous post. I was trying to use the same formulas but I had no luck getting them to work in excel. here is the question. You are going to roll four twenty-sided dice. If the rolls total to 20 or less, roll two more twenty-sided dice and add that to the total. For instance, if the total of my four die rolls is 32, then that is the score of the game. If the total is 17, then I roll two more dice and add that to the total. If these two bonus dice total 20, then the score of that game is 37. Of ten thousand games, what is the average score?

JoshH · 2013-04-26 18:34:09

I am more interested in know how to actually set this up and what the problems are called more than anything. I really want to develop my math skills.

bobbym · 2013-04-26 18:35:17

believe it or not it seams someone already posted the question in a previous post.

Where?

JoshH · 2013-04-26 18:40:03

wont let me post up the whole link

http://www.mathisfunforum.com/viewtopic … =17437&p=1 inserted by mod.

Bob · 2013-04-26 19:45:31

hi JoshH

I don't remember that post. But then I got a surprise. Apparently some guy calling himself Bob Bundy posted some Excel formulas for this.

You say you've had no luck getting those formulas to work in Excel. Odd. My post definitely used Excel. From the date it must have been the 2007 version.

So what didn't work?

Bob

bobbym · 2013-04-26 21:08:43

I remember it now, the exact analytical answer is in post #9. I did not write down the gf and now do not have any idea how to do it.

JoshH · 2013-04-26 21:19:31

hey guys I ended up doing the second problem on that post in a long format with excel going down and doing 10k simulation runs of 4 sided dice then nest to it a column with additional rolls if less than twenty. I then go the average score which was 41%. just wondering if my formulas where right here is what I typed up.

For Rolls of 4 Twenty-sided Dice I used the formula. =RANDBETWEEN(1,20)+RANBETWEEN(1,20)+RANBETWEEN(1,20)+RANBETWEEN(1,20)

Then the next column reads.

=IF(B4<20,+RANDBETWEEN(1,20)+RANDBETWEEN(1,20))

Then to get my average I used.

=AVERAGE(B4:B10003,C4:C10003)

now I don't know how to reduce the additional numbers in excel so I get averages that read like 41.633405 I'd like to just have the average be a whole number w/o decimal point.

I am now currently working on the heads or tail portion. I am formatting the problems this way because my instructor posted a video using these formats. I know there is a short cut way but to avoid any confusion on my part I like to try to keep this as simple as possible. If you can help me with the heads or tails formulation I would be greatful.

Thanks a mil for all your feedback as well.

Sincerely,

Josh

Bob · 2013-04-26 23:02:58

hi Josh

"For Rolls of 4 Twenty-sided Dice I used the formula. =RANDBETWEEN(1,20)+RANBETWEEN(1,20)+RANBETWEEN(1,20)+RANBETWEEN(1,20)"

I'm assuming that formula is in B4. And the RAN(D missing)BETWEEN is just a typo. In which case that's Ok so far.

"Then the next column reads.

=IF(B4<20,+RANDBETWEEN(1,20)+RANDBETWEEN(1,20))"

Strictly the B4<20 doesn't satisfy the question as it says 20 or less. The random numbers are whole numbers so switch this to B4<21 so that you pick up the case of score = 20 as well.

So the B column has the total of four throws, repeated 10000 times.
And the C column has the extra 2 throws when B is 20 or less.

So far so good.

"Then to get my average I used.

=AVERAGE(B4:B10003,C4:C10003)"

Unfortunately this won't work to get the right answer. You want <grand total> divided by 10000. Using the average command like this will do <grand total> divided by 20000 as it counts all the cells you have specified.

Two ways round it: (i) Make a new column, say, D = B + C and just average the D column.

OR (ii) use SUM() instead of AVERAGE() so you get the correct <grand total> and then do a separate /10000 for the correct division.

With spreadsheet work like this, I recommend that you just try a few simulations first and check the calculations by hand. That way you can check that your formulas are doing the right job.

I think there is a way to condense the 10000 lines into one but I've never used it. Another member, phrontister, will probably know how to do this so I'll ask him to check out this post.
Bob

JoshH · 2013-04-27 02:44:11

Hey guys just woke up! Thanks a Million bob! I was up till 5 am this morning working on the excel problems. I feel like I am honestly learning it and you all are being very helpful.
I will go ahead and work on what you just posted up and let you know how it works out!

Sincerely,

JoshH

JoshH · 2013-04-27 03:33:47

alright I am currently working on a problem with 10k sims in a game where you have 10 chances to flip a heads or tails coin to win a dollar the rule to win is you must roll heads four times in a row. I made the 10k sim cells then went across over ten columns with the command of =RANDBETWEEN(0,1). now what is left is figuring out how to add the ten cells in the next column to show a winning or losing roll and also have a sum average at the end to see the probability of winning in this game.

JoshH · 2013-04-27 05:21:40

Hey Bob I was trying to run the coin simulation in excel and while I get the first bar correctly working the next 3 bars that give you results seam to not work. I am using excel on a mac.

Bob · 2013-04-27 05:24:46

hi Josh

Just reading up what you've said. Back in a moment.

Bob

JoshH · 2013-04-27 05:29:40

thanks a bunch if you think screen shots would help you out let me know I will screen cap the issue I am having.

Bob · 2013-04-27 05:31:39

while I get the first bar correctly working the next 3 bars that give you results seam to not work

?? Not understanding you. If you let 0 - tails and 1 = heads then a win occurs when you get 1111 at some point in the ten rolls.

eg 0101111..... or 0000001111 or 10101111 etc.

I think I've met this before. There's a Excel function that allows you to look for an instance of "1111" in a ten character string. So the trick would be to do the ten 'throws' and then convert the numbers into strings instead ie as if each number is a letter.

Bob

Bob · 2013-04-27 05:33:03

Yes an image would help. Can you post here yet or point to an image elsewhere.

Bob

JoshH · 2013-04-27 05:48:29

I believe I might be able to post. the picture here let me see.

Math Is Fun Forum

#1 2013-04-25 14:39:51

Greetings!

#2 2013-04-25 14:43:47

Re: Greetings!

#3 2013-04-25 20:54:54

Re: Greetings!

#4 2013-04-26 00:17:56

Re: Greetings!

#5 2013-04-26 00:40:22

Re: Greetings!

#6 2013-04-26 17:33:22

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#7 2013-04-26 17:42:10

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#8 2013-04-26 18:25:17

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#9 2013-04-26 18:29:00

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#10 2013-04-26 18:31:19

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#11 2013-04-26 18:34:09

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#12 2013-04-26 18:35:17

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#13 2013-04-26 18:40:03

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#14 2013-04-26 19:45:31

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#15 2013-04-26 21:08:43

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#16 2013-04-26 21:19:31

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#17 2013-04-26 23:02:58

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#18 2013-04-27 02:44:11

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#19 2013-04-27 03:33:47

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#20 2013-04-27 05:21:40

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#21 2013-04-27 05:24:46

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#22 2013-04-27 05:29:40

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#23 2013-04-27 05:31:39

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#24 2013-04-27 05:33:03

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