Breaking Apart Numbers to Add Two-Digit Numbers

Khan Academy

This educational video demonstrates a mental math strategy for adding two-digit numbers by decomposing addends and rearranging them to form 'friendly numbers' (multiples of ten). The narrator walks through two specific examples: 53 + 17 and 41 + 9. In the first example, 53 is broken down into 50 + 3, and the 3 is then combined with 17 to make 20, turning the difficult problem into the much simpler 50 + 20. The video highlights key mathematical concepts including place value, decomposing numbers, and the associative property of addition (grouping). By using parentheses visually, the video explicitly shows how changing the order of operations can simplify mental calculation. The second example transitions to a standardized test-style format, guiding viewers on how to fill in the blanks for a step-by-step solution. For educators, this resource serves as an excellent tool for teaching number flexibility and mental math fluency. It moves beyond standard algorithms to help students understand the underlying structure of numbers. It is particularly useful for students who struggle with carrying/regrouping in their heads, offering them a logical alternative that leverages making tens.