Students are introduced to addition expressions to represent two-digit numbers. To ensure that students have a deep understanding of decomposing numbers, they are asked to consider expressions like \(3 + 70\) in addition to the traditional standard form (\(70+3\)). Students use their base-ten understanding of two-digit numbers to add multiples of ten to any two-digit number and mentally find 10 more or 10 less than any number (that is, \(52 + 10\) or \(32 − 10\)). They see that the value of the tens digit changes based on the number of tens added or subtracted, but the value of the ones digit remains the same.

1.4 Family Support Material