standard_description: Add within 100, including adding a two-digit number and a one-digit number, and adding a two-digit number and a multiple of 10, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method and explain the reasoning used. Understand that in adding two-digit numbers, one adds tens and tens, ones and ones; and sometimes it is necessary to compose a ten.
problem_activity: Problem 1
a.   Solve.
10
$$\times$$
23 = ___________
10
$$\times$$
450 = ___________
10
$$\times$$
10,870  = ___________
b.   What do you notice about Part (a)? What do you wonder?
c.   Use your conclusions from Part (b) to find the solutions below.
___________
$$\times$$
10 = 5,090
60,200
$$\div$$
10 = ___________
___________
$$\div$$
10 = 3,050
20,008
$$\times$$
___________ = 200,080
Problem 2
There are about 39,000 fourth graders in Mississippi and about 390,000 fourth graders in Texas. There are about 3,900,000 fourth graders in the United States.
a.   How many times more fourth graders are there in Texas than in Mississippi? How many times more fourth graders are there in the United States than in Texas?
b.   There are about 3,900 fourth graders in Boston, MA. How many times more fourth graders are there in the United States than in Boston?


aligns: no