Tomas Lewis

December 16 2020

Photo by Thought Catalog on Unsplash

Addition involving money is often found in math textbooks as word problems involving people with names like Jack and Rita who buy a few things and then want to find out how much they spent. This doesn't mean that the math you have to do is different from other types of addition, but it does mean you have to work out first what the sum you are being asked to do is, and then work on the sum itself.

Say we have 2 things that cost 12 cents each. To know the total cost, we simply add the 12 cents twice to get 24 cents. If the 2 items cost different amounts like 22 cents and 34 cents, we can still add up those 2 amounts to get a total cost quite easily.

22¢ + 34¢ = 56¢

If the sum of all the coins goes over 100, then we need to deal with both dollars and cents. Divide the answer in cents by 100 to get the number of dollars, and the remainder is the number of cents.

55¢ + 46¢ + 33¢ = $1.34

When we want to understand math problems that come as words and sentences, we need to read carefully through the text and create a sum that takes the number information out of the text and puts it in a sum. For instance, in the text

"Apples cost 25 cents each. Jack buys 2 apples and Jill buys 3 apples."

we can see that the thing we are interested in is the cost of the apples, and the numbers we need to sum are (2 + 3) x 25¢. First we want to get the total number of apples so we add up the 2 (the number of apples that Jack has) and the 3 (the number of apples that Jill has). Written as a sum this will obviously be

2 + 3 = 5

So we can know that the total number of apples is 5. Since we know that each apple costs 25 cents, to find the total cost of the apples we have to add 25 five times, or more simply, we can multiply 5 by 25.

5 x 25¢ = 125¢

If this was ordinary addition, we would now be finished but because we are dealing with money, we need to do one more step. We know that 100 cents makes $1 and since our answer is bigger than 100, we need to split the answer up in to the number of notes and the number of coins left over. In this case, we have 1 dollar with another 25 cents left over, so the sum should really look like this:

5 x 25¢ = $1.25¢

If the numbers you have been asked to add are bigger, then add the dollars first, then add the cents. If the value of the cents goes over 100, add 1 to the dollars and the remainder will be the cents.

$3.55¢ + $2.66¢ = $6.21¢

You can try out your new skills here at ** Free Math Games**. Go to Start → select your grade, year or age → select Addition → select Word problems.

Kindergarten math | Elementary math | Secondary math

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