A number line turns adding and subtracting into jumps: jump right to add and left to subtract. You learned to read number lines in Numbers on a Number Line.
Por qué funciona
27 is 2 tens and 7 ones, so you can jump 10, 10 and then 7. Splitting the 7 into 4 and 3 lands on 70 first, a friendly number. All the jumps together still add up to 27.
Ejemplo resuelto: Add with jumps
Find $46 + 27$.
- Start at 46. Jump +10 to 56, then +10 to 66.
- Jump +4 to 70, then +3 to 73.
Respuesta: $46 + 27 = 73$
Ejemplo resuelto: Subtract with jumps
Find $83 - 35$.
- Start at 83. Jump −10 three times: 73, 63, 53.
- Jump −3 to 50, then −2 to 48.
Respuesta: $83 - 35 = 48$
Ejemplo resuelto: Find the distance
How far is it from 58 to 92?
- Jump +2 from 58 to 60.
- Jump +30 to 90, then +2 to 92.
- Add the jumps: $2 + 30 + 2 = 34$. So $92 - 58 = 34$.
Respuesta: $34$
Idea clave
On a number line, adding jumps right and subtracting jumps left. Jump by tens, then ones, and aim for friendly numbers that end in 0.
Error común
Counting how many jumps there are instead of adding their sizes. From 58 to 92 there are 3 jumps, but they are 2, 30 and 2, so the distance is 34. Check: $58 + 34 = 92$.
Grown-up tip: A tape measure on the floor makes a great number line to hop along.