Word problems are troublesome for many students. So well-meaning teachers have come up with strategies to help solve them.
One strategy is to use keywords from the word problem to determine which operation to use.
Another strategy some teachers use along with key words is called CUBES which stands for
Circle the the numbers
Underline the question
Box the key words
Evaluate the steps to use
Solve and Check
At first, it seems like a good idea to use these strategies. Students are looking for the information needed to answer the question and most of the time they get the correct answer.
Focusing on getting the right answer and moving on, fosters the idea that a correct answer means mastery and this is simply not true.
We should expect more of our students. Students need to be able to explain what the question was asking, why a strategy was chosen, and what the answer means.
Let’s look at a few examples and see why keywords and CUBES don’t work.
Students don’t try to make sense of the word problem.
Billy has 5 marbles. Joe has 8 marbles. How many more
marbles does Joe have?
Students who use CUBES often don’t actually read the word problem. They would circle the numbers 5 and 8, box “more”, and underline the question all without thinking.
The last two steps - Evaluate and Solve and Check - are usually ignored.
Students can’t evaluate the steps to use or check if the answer makes sense if they haven’t read the question closely and thought about the situation.
They can lead students down the wrong path.
In the marble word problem above, the word “more” would have been boxed, so students would use addition to solve the problem.
However, this problem is a subtraction problem. Joe has 8 marbles so he has 3 more marbles than Billy’s 5 marbles.
Some word problems don’t have any keywords.
Kim went shopping for a new hat. She gave the clerk $20 and
received $12 in change. What was the price of the hat?
Since there are no keywords, many students would pluck the numbers out and “do something” with them.
Some students would use addition because it’s easier for them.
Others would get frustrated and skip the problem entirely. They have been taught how to solve word problems by using a set of steps which can’t be used.
It’s no wonder why kids dislike word problems!
To solve this word problem correctly, students must think about what happens when we go shopping and what “$12 in change” means.
Then they would understand that they need to subtract $12 from $20 to figure out the hat cost $8.
Multi-step word problems can’t be solved.
Mrs. Jenks and her 3 children go to the movie theater one afternoon.
Adult movie tickets cost $8 and children’s movie tickets cost $5. If they
spend $15 at the snack bar, how much did they spend altogether?
Students using CUBES would circle 3, 8, 5, and 15 and box “altogether” which is the keyword that means they should add the numbers together.
However, students would first have to multiply the cost of the children’s tickets by the number of children to get the total cost of the children’s tickets.
Then they would have to add the total cost of the children’s tickets, the cost of one adult ticket, and the cost of the snacks to find how much was spent altogether.
They don’t prepare students for advanced concepts.
92 fluid ounces of laundry detergent costs $9.99 while 138 fluid
ounces of the same brand costs $17.99. Which size of laundry
detergent is the better buy?
Students using CUBES would circle 92, 9.99, 138, and 17.99. There is no keyword to box so there is nothing to help them to answer the problem.
This is a ratio word problem. To solve, students must understand that they need to find the unit price of each size of laundry detergent - by dividing the cost by the number of fluid ounces - to figure out which one is the better buy.
Strategies like Keywords and CUBES leave students unprepared and with none of the resources needed to answer word problems.
Check out this post about an effective alternative to teach word problems.
Let me know what your experience has been using keywords and CUBES. Have you found these to be helpful to students or have you changed your approach to solving word problems?