Strategy for helping first-graders add two numbers within 20:

• A. Encouraging students to decompose one of the numbers so it can make a ten with the other number.
• B. Relying solely on memory of facts up to 20.
• C. Using only abacus without writing.
• D. Ignoring Place Value and counting on fingers.

Answer: (A)

This question focuses on using a make-a-ten strategy to add numbers within 20. The idea is to decompose one addend so that it forms a complete ten with the other addend, making the calculation easier to handle.

When you see two numbers to add, look for a way to pair part of one number with the other to reach ten. Break one addend into two parts, where one part adds to the other number to make ten, then add the remaining part. For example, with 7 and 8, take 3 from 8 to pair with 7 and make 10, then add the leftover 5 to get 15. This approach leverages the base-10 structure, helps students do mental math, and builds flexible number sense for more complex problems later.

Other options don’t fit as well because relying only on memorized facts up to 20 isn’t robust for all pairs and can fail without recall. Using an abacus without writing won’t develop quick mental strategies or transfer to mental math. Ignoring place value and counting on fingers misses the ten-based structure essential to efficient addition and long-term fluency.