What is zero? Zero and place value
A math problem showing place value How can you add big numbers without an abacus? You still group the sheep (or whatever) just as you did when you were using the abacus, but [...]
A math problem showing place value How can you add big numbers without an abacus? You still group the sheep (or whatever) just as you did when you were using the abacus, but [...]
A boy walking backwards Subtracting numbers is just the same as adding them, only walking the other way along the number line. To subtract 3 from 8, you start on the number [...]
Walk along a chalk line The four basic things you do with numbers are addition, subtraction, multiplication, and division. Each of these is basically a way of describing how fast you are moving along [...]
Walk along a chalk line To get to understand the number line better, mark out a line on the playground or on the sidewalk outside your house with chalk. At the middle of [...]
A number line is infinite in both directions. When people say that addition is commutative, that means that it doesn't matter what order you add up the numbers. 3 + 6 [...]
A number line is infinite in both directions. Adding numbers is like walking along a path, the number line. To add two small numbers, like 7 + 4, you can just [...]