Number Line Explorer

Arithmetic · Axiom Academy

Every whole number has a home on one straight line — and once you can see them in order, adding and subtracting become nothing more than hops left and right. Numbers live in order on a line A number line is just a straight road with the whole numbers spaced evenly along it: 0, then 1, then 2, and on forever. Smaller numbers sit to the left, larger ones to the right — so the picture itself tells you which number is bigger before you do any arithmetic. Watch the marker walk the line from 0. Each hop moves it one tick to the right and adds one to its position — so the order you count in is exactly the order the numbers appear, left to right. Counting up is the same as stepping right: every hop is +1, and the marker never skips a number. Drag the marker to any whole number. The one just to its left is the number before it; the one just to its right is the number after it. Because the line is in order, every number sits snugly between the two it's nearest to. 3 is to the left of 4, and 5 is to the right — so 3 < 4 < 5. Adding and subtracting are just hops Set a starting number and a number of steps, then play the hop. Moving right adds; moving left subtracts. So 5 + 3 is a three-step hop right that lands on 8, and 8 − 3 is a three-step hop left back to 5. Drag the sliders, then watch the marker hop — the direction is the whole difference between adding and subtracting. One line, the whole of arithmetic

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