All of the Following Could Be Examples of Invented Strategies

Multiple Choice

All of the following could be examples of invented strategies for obtaining the sum of two-digit numbers EXCEPT:

A) Adding on tens and then ones (For example,to solve 24 + 35,think 24 + 30 = 54 and 5 more makes 59.)
B) Using nicer numbers to estimate (For example,to solve 24 + 47,think 24 is close to 25 and 47 is closer to 45 so 24 + 47 = 25 + 45 = 70.)
C) Moving some to make 10 (For example,to solve 24 + 35,move 6 from 35 to make 24 + 6 and then add 30 to the remaining 29.)
D) Adding tens and adding ones then combining (For example,to solve 24 + 35,think 20 + 30 = 50 and 4 + 5 = 9 so 50 + 9 = 59.)