Number Line Hop

The big ideas

What the levels teach, in grown-up words.

• A number line keeps numbers in order. Every number has its own place, one hop apart. That is why you can find a missing number from its neighbors.
• Adding is hopping forward; taking away is hopping back. 3 + 2 means start on 3 and hop forward 2. 6 − 2 means start on 6 and hop back 2. Where you land is the answer.
• Tens are big hops. To get to 43, take four hops of ten and three hops of one. Adding 13 is one big hop and three little ones.
• Halfway means the same distance from both ends. 35 is five hops from 30 and five from 40. 50 is halfway between 0 and 100.
• Rounding means hopping to the closest ten. 47 is closer to 50 than to 40, so it rounds to 50. A number ending in five is exactly in the middle, and the rule is to round up.

Try it at home

Quick experiments that match the game.

1. Floor number line. Lay out numbered cards or chalk a line from 0 to 10 and hop along it. Start on 4, hop 3: where are you?
2. Hop back. Stand on 8 and hop back 3. Then try 10 take away 4. Say each number as you land on it.
3. Guess the halfway. Pick two numbers like 20 and 30 and guess the number halfway between. Check by counting steps from each end.
4. Rounding game. Call out numbers like 23, 58 and 75. Hop to the nearest ten and say which way was closer.