How to Solve Word Problems Involving Money
Welcome to this Mometrix lesson on word problems with money. Usually word problems with money will deal with purchasing something, taxing something, or maybe deducting something from a total price. When reading a word problem, it could get overwhelming, seeing as you’re expected to solve a paragraph of text; surely that’s not math, right? If this is your thought process, well, I’ve got some helpful tips for you! For starters, word problems are not all that scary and actually quite easy to maneuver once you know how, and second, yes, math problems can exist in a block of text! Today, we’re going to break down the scary assumptions that come with solving money word problems and learn how to solve them without hesitation!
The best way to learn something is to try it for yourself, so let’s start by looking at a problem I’ve created:
You and your friends want to order a large pizza for $14.99. You have a budget of: $20. Considering the tax of 4% and the tip at 30%, will you have enough money to buy the large pizza?
When starting a word problem, a good rule of thumb is to identify information that is necessary and information that is unnecessary in the problem.
Your budget of $20 is unnecessary information starting out, however it will become important once we solve the problem. At this point, we really only need to focus on the price of the pizza and finding out what the tax is. Then we can move on from there.
First, we need to determine how much our tax will add onto the bill. To do this, we need to multiply 14.99 with 4%, or .04. (14.99)(.04)=.5996
Next, we need to add .5996, our tax, to 14.99, our total.
To keep our number most accurate, we won’t round to the nearest cent until we have reached our final number.
So, we have .5996+14.99=15.5896
Now that we know the sum of the original total and our tax, we need to factor in a 30% tip.
We need to multiply 15.5896 with 30%, or .30. (15.5896)(.30)=4.67688
Lastly, we need to add 4.67688 with 15.5896 to reach our total number 15.5896+4.67688=20.266. After rounding up, we reach 20.27.
The total for your order would be $20.27. You would be $.27 short of being able to order a pizza for you and your friends. I’d say it’s time to start checking the couches for spare change!
When we break down word problems into manageable steps, they seem a lot less daunting, right? Next time you’re given a word problem with money to solve, be sure to start with what is known, what is necessary, and what is unnecessary information in the word problem. Identifying these things will help to clear up your understanding of what is being asked in the problem. After identifying the necessary information needed to solve the problem, perform the operations outlined in the question to reach your total(s) and compare your answers.
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All of the items listed below, except for one, are helpful strategies to remember when solving word problems in math. Which item is NOT a helpful strategy?
Identify the relevant information that is necessary to solve the problem.
Perform the operations that are outlined in the question.
Compare and check your final answer to see that it is reasonable.
Always assume that every number provided in the text is relevant and useful for solving the problem.
There will often be irrelevant information provided in math word problems. Make sure not to assume that all numbers or information provided in the text is crucial for solving the problem.
Determine the piece of information that is irrelevant to solving the problem.
Jane is purchasing dog food at her local pet store. Jane notices that the store is having a 20% off sale on dog toys. Jane sees that Brand A of dog food costs $45 for a 20 pound bag, and Brand B of dog food costs $49 for a 22 pound bag. Which brand of dog food is less expensive when considering dollars per pound?
Brand A costs $45 per pound
Brand B costs $49 per pound
The store is having a 20% off sale on dog toys
All of the information provided is crucial for solving the problem.
The price per pound for Brand A and Brand B is crucial for solving the problem. This information is what will allow us to determine which brand is the better deal. The fact that the store is having a 20% off sale on dog toys is irrelevant to the problem.
Dianne and Gary order sushi from their favorite restaurant for Gary’s birthday. The bill is $45.50 before the tip. Dianne offers to pay for the entire meal plus tip. She only brought $55 in cash, and she plans on leaving a 20% tip. Gary says that he has $44 in his wallet and he is willing to help with the bill. Does Dianne have enough to pay for the whole meal plus tip, or will Gary need to contribute to the bill?
Yes, Dianne will have enough to pay for the entire bill plus tip.
No, Dianne will not have enough to pay for the entire bill plus tip. Gary will need to contribute in order to cover the bill.
Information that is irrelevant: Gary says that he has $44 in his wallet and he is willing to help with the bill. (This piece of information can be ignored because it is not crucial for solving the problem).
The tip can be calculated by multiplying $45.40 by 20% or 0.2. $45.50 × 0.2 = $9.10 tip. This can be added to the bill in order to determine the total cost of the meal.
$9.10 + $45.50 = $54.60
Dianne has $55, so she has enough to pay for the entire meal plus tip.
Eugene spends $24 on toy cars. He purchased 6 cars. His friend Julian spends $28 on toy cars. If each car is the same price, how much did Eugene spend on each car?
$3 per car
$4 per car
$5 per car
$6 per car
Information that is irrelevant: His friend Julian spends $28 on toy cars.
The important information in the text is that Eugene spends $24 on 6 cars. If each car is the same price, then we can divide $24 by 6 in order to determine the price per car. $24 divided by 6 is 4, so $4 per car.
Jason has a part-time lawn mowing job in the summers. This week Jason mows four lawns on Monday, five lawns on Tuesday, and three lawns on Thursday. He earns $35 per lawn, and he always saves 20% of the money he makes per lawn into his savings account. On Friday Jason spends $12 on ice cream with his friends. How much money did Jason place in his savings account this week?
$84 is placed in his savings account.
$420 is placed in his savings account.
$100 is placed in his savings account.
$35 is placed in his savings account.
Information that is irrelevant: On Friday Jason spends $12 on ice cream with his friends.
Jason earns $35 per lawn, and he mows 12 lawns this week. $35 times 12 is 420, so he earns $420 this week. 20% of this will be placed in his savings account. 0.2 times $420 is 84, so $84 is placed in his savings account this week.