Standard - NY-1.NBT.4:
Add within 100, including

• a two-digit number and a one-digit number,
• a two-digit number and a multiple of 10.

Use concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction.

Understand that in adding two-digit numbers, one adds tens and tens, ones and ones, and sometimes it is necessary to compose a ten.

Relate the strategy to a written representation and explain the reasoning used.

Standard - NY-1.NBT.5:
Given a two-digit number, mentally find 10 more or 10 less than the number, without having to count; explain the reasoning used.

Standard - NY-1.NBT.6:
Subtract multiples of 10 from multiples of 10 in the range 10-90 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 used to a written representation and explain the reasoning.