Solving Problems that Involve Subtraction

Hi, kids. This e-tivity is about understanding what mathematical operation is needed to get the answer of a word problem. It's the second from a series of e-tivities about problem solving. By the end

• you will be able to identify what words indicate subtraction,
• you will learn how to subtract fractions.

Average online time: 25 min

Average offline time time: 10 min

1) What words do you think indicate subtraction in a word problem?
Share with your classmates your ideas, write down your message and the click the shout button

2) Consolidating our thinking

Let's watch the following video, please turn on your speakers



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3) Solving a word problem

Remember that there are at least three questions you need to ask yourself in order to solve a word problem:

1) What numbers are needed to answer the question?

2) What mathematical operation(s) is/are needed?

3) Does my answer make sense?

María is placing some wood fence along a path that is  10   1/3 feet long.  After finishing her daily work, she has already completed  5   2/3  feet. How many feet are there left for completing the fence?

a) What numbers do I need to answer the question? 10  1/3 and 5  2/3

b) What mathematical operation is needed? subtraction because of the words how many....are left

c) Subtracting 10  1/3  &  5  2/3

d) Answering the question.  There are left 4  2/3 feet.

5) Your Task

You need to invent a word problem that requires subtraction to be solved (hint: use one of the key words here explained). Once you have invented your problem, you need to solve it by following these four steps:

a) Understanding: What numbers do I need to answer the question?

b) Planning: What mathematical operation is needed?

c) Solving the problem

d) Answering the question

Do not forget to post your comment including your word problem and the steps a), b), c), and d) you used to solve it.

See you around!