Grade Two Math | Grade One Math |
This week we focused on the special case of subtracting from multiples of 100 and numbers with zero in the tens place. For example, 300 can be decomposed into 2 hundreds and 10 tens, then 1 ten is decomposed into 10 ones (two steps); or 300 can be renamed directly as 2 hundreds, 9 tens, and 10 ones (one step). In each case, students use math drawings to model the decompositions and relate them to the written vertical form, step by step. | Students are learning about place value and adding larger numbers. In this unit we are using linking cubes as a concrete representation of the numbers, writing a matching number sentence, and writing the total in a place value chart. As they add cubes, students see that sometimes you make a new ten, for example, 33 + 7 = 40, or 4 tens. students recognize single-digit addition facts as they solve 15 + 2, 25 + 2, and 35 + 2. When adding 33 + 4, students see that they are adding 4 ones to 3 ones, while the tens remain unchanged, to make 3 tens 7 ones or 37. When adding 12 + 20, students see that they are adding 2 tens to 1 ten to make 3 tens 2 ones or 32. In both cases, one unit remains unchanged. In addition to cubes, we use using dimes and pennies to model each addend. For instance, students model 14 cents using 1 dime and 4 pennies, and add 2 additional dimes or 2 additional pennies. |