Visually representing percent word problems (Day 2)

Have students work on the following problem…. A store offers a 20% discount on tires.  The original price of the tires cost $300.  How much is your discount?  What is the sale price?

I chose this problem to see if students could apply their learning from yesterday and to also set them up for today’s lesson.  Students may need help understanding that a discount means a lower price.  You may need to ask students “what are you trying to find”?  I’m looking for them to say that they have to find 20% of $300.  Ask them if there is a tool they could use to help them solve this problem?  Encourage students to use a diagram to help them solve this problem.  (SMP 1 and 2)  The stretch in this problem is to get the students to recognize that when they find the 20% it represents to discount and in order to find the sale price, they will need to subtract.

Let students have a moment to start independently.  After a few minutes, allow them time to come up with a strategy with a partner.

This will be a review of yesterday’s learning.  I’m going to give the students several problems where they need to find the missing part.   I’ve chosen both mathematical and real-world problems to help represent this context.  Give students time to work on this alone.  As students are working, I’m going to be targeting the struggling learners.  I will be working with them to find a strategy that makes sense and encouraging them to use only that strategy.  I will also be working with them on benchmarks.  For example, if I’m trying to find 40% of a number, I know that 40% is close to 50%.  50% means ½ and I can find ½ of any number so I know my answer is around…  I will be modeling this type of thinking for them. 

The students will be working on problems that are missing the part.  For example, if 75% of the budget is $1200, what is the total budget?

The students will be using a strategy to help them solve (tape diagram, ratio table, double number line).  I will be modeling a few for them, then they can work independently on the rest.

It will be important that you refrain from mentioning any “tricks” to find the answer.  We want the students to be able to represent this visually to get a solid understanding of ratio relationships. 

The students will be working on finding the percent using a diagram of their choice.  For example, if Michael read 60 pages of his 300 page book, what percent of the book does he have completed?  Again, I will be modeling with each strategy and then letting the students try some on their own.

Percent problems have 3 parts: the part, the percent, or the whole.  Given any two parts, we can solve percent problems.  In the following scenarios, decide whether the part, percent or whole is missing and tell how you know. (If time permits, you can solve)  I’m using this as my closure so that the students can see that as long as we have any 2 pieces, we can solve a percent problem.

1.  60% of 50 = _______________   
2. ________________ of 50 is 30
3. 20% of _________________ is 90

After students have had time to figure out their answers, give them time to discuss with their tablemates.  Open this up for group discussion afterwards.