CA-64 Chapter 3 Addition and Subtraction m CLASS ACTIVITY 3-H Reasoning to Add and Subtract [E53 CCSS SMP2 1. John and Anne want to calculate 253 99 by first calculating 253 100 = 153 John says that they must noOw subtract 1 from 153, but Anne says that they must add to 153. a. Draw a number line (which need not be perfectly to scale) to help you explain who 1s right and why. Do not just say W hich answer is numerically correct; use the number line to help you explain why the answer must be correct. b. Explain in another way who is right and why. 2. Dakota says they are thinking of 253 99 as how much they need to add to 99 to make 253. With Dakota's view of 253 99 as an unknown addend or a difference in a comparison, what reasoning might they use to calculate the answer? 3. Jamarez says that he can calculate 253 99 by adding 1 to both numbers and calcu- lating 254 100 instead. a. Draw a number line (which need not be perfectly to scale) to help you explain why Jamarez's method is valid. b. Explain in another way why Jamarez's method is valid