Students fluently recall addition and subtraction facts within 20, including zero, doubles, near-doubles, make-ten strategies, missing values, and adding or subtracting 10, 100, and multiples of 10 using place value through 1,000. They add and subtract two-digit numbers, including one-digit addends or subtrahends, with and without regrouping, add three two-digit numbers, and use partial sums and place-value representations for addition within 1,000. They solve joining, separating, comparison, part-part-whole, missing-addend, and two-step problems within 100, write related equations, and informally estimate sums and differences using friendly tens or hundreds through 1,000.