Fraction Sums and Differences

Use Check-In: Questions 5–7 on the Fraction Sums and Differences pages in the Student Guide to summarize the lesson. In Question 5, Grace uses an incorrect algorithm to add fractions. Make sure that when students discuss this question, they think about whether Grace's answer is reasonable, not just whether or not she did the calculation correctly.

In Question 6, students estimate sums and differences by locating fraction sums and differences on the number line. Remind students that even though they are learning a way to calculate using common denominators, they should continue to be able to estimate fraction sums and differences. They should also continue to calculate simple sums and differences without finding common denominators if they are able to do so with mental math (e.g., visualize that 1/3 + 1/6 = 1/2). In Question 7, students find exact answers and compare their estimates to the answers to check for reasonableness.