Today we played a game titled "Least to Greatest." Children worked in teams to put 6 sums like 39+39, 49+27, 16+17, and 19+45 in order from least to greatest. The children used several different strategies to achieve this task.
Many children started by comparing addends. For example, when comparing 39+39 and 16+17, it is clear that 39+39 is greater because both addends are greater than the addends in 17+17.
Often times children tried rounding to the nearest ten. For example, 49 rounds to 50 and 27 rounds to 30, so 49+27 would be about 80. Sometimes, this type of estimation did not give children an close enough estimate.
So, children sometimes added the tens digit of each addend. To get a closer estimate, they would look at the ones place. If the sum of the ones place was greater than 9, they would know that the tens place would be one greater. For example, when estimating 19+45, students would add 1+4 (from the tens place.) They would look at the ones place (9+5) and see that the sum is greater than 9. Therefore, the estimate would be in the sixties.
Look in your child's folder tomorrow for a copy of this game. Play it with your third grader at home! :o)
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