3.NBT. Grade 3 - Number and Operations in Base Ten
3.NBT.A. Use place value understanding and properties of operations to perform multi-digit arithmetic.
3.NBT.A.1. Use place value understanding to round whole numbers to the nearest 10 or 100.
3.NBT.A.2. Fluently add and subtract within 1000 using strategies and algorithms based on place value, properties of operations, and/or the relationship between addition and subtraction.
3.NBT.A.3. Multiply one-digit whole numbers by multiples of 10 in the range 10–90 (e.g., $9 \times 80$, $5 \times 60$) using strategies based on place value and properties of operations.