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Basic Math/Counting back change


QUESTION: Dear Mr. Zalewski,

I've had a lot of retail jobs. Sometimes a customer will decide to give me some loose change after they've given me a $10.00. I can count money. I can add, subtract, multiply and divide pretty good on paper. I just struggle hard with making change in my head. Do you have any recommendations for adult resources so I can improve my confidence in making change.   

Also, I was chosen to run an lunch errand for co-workers years ago. They each gave me various $10 and $20 bills, with varying amounts for the food they requested. I think I pretty much botched the change. If you were in that situation, how would you make sure that each person got the correct change back?

Thank you for taking the time out of your busy schedule.



ANSWER: Hello, David.

Here is a website which may help you with your problem:

For the second question, if I were in that situation, I would have made sure that I remembered what each person wanted and how much money they gave me (writing down the information if there were a lot of people involved). At that point, giving back proper change is easy: simply look at your receipt, determine the value of each person's order, then subtract those amounts from the dollar amounts that your co-workers gave you.

Any further questions, please ask.


---------- FOLLOW-UP ----------

QUESTION: Thank you, John.

I went to the website. It wasn't very clear for me.

As for the second question, making sure of each person's order was the only thing I got right. I think somehow I used one or more of the $20.00 bills for the combined bill, which left an uneven return for everyone's exact change. There was left over money given to me that I did not use is what I am saying. Can you see now how I might've done it better?

Thank you for your time.



Hello, David.

I guess what you could do is carry each person's bill in a separate bag or whatever, then, pay for each item separately. Doing this will prevent the bills from being mixed and it will be certain that each one will be used.


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John Zalewski


I can help you solve problems involving fractions, decimals, ratios, and algebra. I can teach you how to do math faster, and even in your head. I can teach math definitions, and help you study, if necessary. Please do not ask any graphing, trigonometry, or calculus questions. Try to work through homework questions before asking for assistance.


I routinely process numbers of all kinds in my head, without need of a calculator.

I was an A math student while in high school.

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