All students were assigned Questions 6–8, and Check-In: Questions 16–17 on the Find Fraction Sums and Differences pages in the Student Activity Book. Choose to discuss some of the questions as a class, or just focus on comparing the problems in Questions 6 and 17.
- Do the problems in Question 6 need exact answers or can you estimate? Explain. (You could estimate for both. Question 6B just asks if the total weight of the boxes is over or under 4 pounds. I can use my estimated weight of Box A and add a little more than 2 pounds for Box B and see that the total weight is under 4 pounds.)
- Can you think of a situation when a very close estimate is needed? (Possible response: You need a close estimate when measuring expensive fabric or materials to make something because you want to have the right amount and you don't want to overspend. You need close estimates when you are determining how much of an ingredient to buy for a recipe so you are sure you have enough but don't have a lot of extra left over.)
- Can you think of a situation when an overestimate is needed? (Possible response: You might overestimate to make sure you have enough money for something. You might overestimate how long it will take you to get somewhere so that you are sure you are not late.)
- Can you think of a situation when an underestimate is needed? (Possible response: You might underestimate the amount of food you have at a party because not everyone will eat it. You might underestimate the number of supplies you need to buy if you already have some.)
- Does the problem in Question 17 need an exact answer or can you estimate? How did you decide?
(exact answer; Possible response: There are clues in the question. We had to find out how much granola was needed for exactly four servings. It said John didn't have extra room in his backpack and had to pack carefully, so an overestimate wouldn't be smart, and an underestimate might not give them enough breakfast. We needed to find how much more granola would fit into John's container.)
- How can you estimate to see if your answer is reasonable? (Possible response: 7/8 is close to 1, so four 7/8 - cup servings are a little less than 4 cups. My answer is 31/2 cups, which is close. There's not much difference between 32/3 and 31/2, so my answer of only 1/6 cup is reasonable.)
Use Check-In: Questions 16–17 with the Feedback Box on the Find Fraction Sums and Differences pages in the Student Activity Book to assess students' abilities to find equivalent fractions [E1]; represent addition and subtraction of fractions with number sentences [E3]; solve word problems involving addition and subtraction of fractions [E5]; choose appropriately from among estimation and computation strategies [E7]; add and subtract fractions [E8]; estimate sums and differences of fractions [E9]; find common denominators and use them to add and subtract fractions [E10]; know the problem [MPE1]; find a strategy [MPE2]; check for reasonableness [MPE3]; and show work [MPE5].
