When you press 7 + 8 =, the answer 15 pops up in a blink. ✨
A calculator is not magic — it follows the same steps you already know, just super fast. In this lesson you'll see exactly how it adds, column by column.
Tap "Next" to start with a tiny but powerful idea:
numbers live in columns.
A calculator never sees "342". It sees three columns: ones, tens, and hundreds. Each spot makes a digit worth more.
Tap each digit to see what it is really worth:
Tap all three to keep going. 👆
300 + 40 + 2 = 342. Same number — just split into columns!
To add 25 + 13, the calculator lines them up and adds the ones column first, then the tens. Let's watch it work.
Ready when you are!
A column can only hold 0–9. If the ones add up to 10 or more, the calculator keeps the ones digit and carries 1 to the next column.
Look at the ones column: 8 + 5 = 13.
13 is bigger than 9. What should the calculator do?
Here's the secret: inside, a calculator only knows two things — a switch ON (1) or OFF (0). It builds every number out of these.
Each switch is worth double the one on its right: 8, 4, 2, 1. Add up the ON switches to make a number.
Flip switches to make the number 11:
Your total: 0
Tip: 8 + 2 + 1 = 11. Find the right switches! 👆
The calculator flips switches like this billions of times a second — that's why it's so fast!
Use the steps: add the ones, carry if needed, then add the tens.
Ones: 7 + 8 = 15 → write 5, carry 1.
Tens: 4 + 2 + 1 carried = 7.
So what is 47 + 28?
Whenever a calculator adds, it follows these steps — just very, very fast:
The "magic" is just neat, careful steps — done a billion times a second. Great work today! 🌟