Add and subtract multiples of 10 from multiples of 10 to 100, including dimes.

This lesson focuses students on number work with tens as they add and subtract multiples of 10 from multiples of 10. Students see that 20 + 70 is the same as 2 tens + 7 tens, and that 80 - 50 is the same as 8 tens - 5 tens.