Adding Single Digits: 7 + 5

Arithmetic · Axiom Academy

EXAMPLE Adding Single Digits: 7 + 5 One addition fact, worked three ways — counting on, making a ten, and combining all. Compute 7 + 5 . We'll find the same sum three different ways — counting on from the larger number, making a ten , and combining and counting all the units — to see why they all agree. Nice work — you found 7 + 5 three independent ways, and every one landed on the same total. Count On: start at the larger addend and count up by the smaller — fastest when the second number is small. Make a Ten: split the 5 as 3 + 2 , use the 3 to reach 7 + 3 = 10 , then add the leftover 2. Regrouping never changes the total. Combine and Count: merge both groups into one collection and count it all — the slow but definitive meaning of addition. Result: 7 + 5 = 12 , no matter which strategy you use. Single-digit sums are the building blocks of all of arithmetic — having several strategies for them makes larger addition fast and flexible.

This is the written version of the interactive lesson above. See the full Arithmetic course.