Lesson 11 — Activity 2: Missing or Extra Information
Completion requirements
Lesson 11 — Activity 2:
Missing or Extra Information
In some problems,
information needs to be found before the problem can be solved.
Sometimes, you may need to find the number of days in the month of
January, the number of minutes in an hour, or the number of grams in a
kilogram before you can solve the problem.
Other times, there will be extra information in the word problem that you do not need. This can be confusing, so you need to read the problems carefully to find out what information you already have, what information you still need, and what information is not necessary to answer the question.
Step 2:Think of a Plan
and
Step 3: Carry out the Plan
Before you begin: Read about the following terms that you will use later in the lesson.
- Information that is given in the problem that is actually needed to solve the problem is relevant information.
- Information that is needed to solve the problem but is not given in the problem is missing information.
- Information that is given in the problem but that is not needed to solve the problem is extraneous information. Extraneous information can also be called extra information.
Tip! Cross out extra information that you don't need in the problem so you don't use it by accident!
Missing or Extra Information
Antonio wants to buy the laptop shown on the right. In January, he earned $400 at his after-school job. He saved $20 of this amount toward the purchase of the laptop. For each month after January, he will double the amount he saved the previous month. In which month will he have saved enough to buy the laptop?
©iStock
All of the following statements are relevant information.
• You know the cost of the laptop, $600.
• You know that he saved $20 in January.
• You know that each month he will double the amount he saved the previous month.
The following is extra or extraneous information because it is not needed to solve the problem.
• You know that Antonio earned $400 at his after-school job.
You need to find which month Antonio will have saved enough to buy the laptop. This is the missing information.
Let's try another one!
Penny works as a server part-time for a popular restaurant. She worked every day this week except for Saturday and Sunday. Her shifts are for 4 hours each. She makes $11 per hour. She only works during the months of June through August. How much money did she make this week at her part-time job?
©Getty Images
All of the following statements are relevant information.
• You know she worked every day this week except for Saturday and Sunday.
• You know that her shifts are for 4 hours each.
• You know that she makes $11 per hour.
The following is extra or extraneous information because it is not needed to solve the problem.
• You know that she only works during the months of June through August. You might want to cross this information out so you don't use it when figuring out the answer.
The following is missing information that you need to find out before you can answer the question.
- How many days did she work this week? You know that she worked every day except for Saturday and Sunday.
- You also know that there are 7 days in a week.
- Therefore, if she worked every day except Saturday and Sunday, she worked 5 days this week.
Now you can answer the question because you have all the information that you need!
4 hours x $11 per hour = $44
$44 x 5 days she worked this week = $220
Penny made $220 this week working at her part-time job.
Self-check!
Try This!
Answer the word problem below. First, find out what information is relevant, what is missing, and what is extra.
When you are finished, click on the tab below to check your answer!
Kendall pitches for his school’s baseball team. Kendall pitches every game, and he averages 5 strikeouts per game. Each game lasts about 2 hours. If Kendall pitches in 7 games during the season, how many strikeouts will he have?
All of the following statements are relevant information.
• You know Kendall averages 5 strikeouts per game.
• You know that Kendall pitched in 7 games during the season.
The following is extra information because it is not needed to solve the problem.
• You know that each game lasts about 2 hours.
The following is missing information.
- How many strikeouts will Kendall have?