K-5 friendly lesson

One small step at a time.Read the idea, try the activity, and celebrate each win as you go.

Add FOUR 2-Digit Numbers

🏢 Build the skyscraper! Three numbers was a mountain, but four numbers is a skyscraper. Don't speed, or the tower will fall!

Do this: Read the concept below, then try the quiz or activity.

Lesson 78 of 186

Concept

Okay, things are getting serious. Stacking FOUR two-digit numbers requires ultimate concentration.

🎯 The Skyscraper Strategy:
Example: 15 + 24 + 12 + 38 = ?
  1 5
  2 4
  1 2
+ 3 8
--------
1. The Long Ones Column: 5 + 4 = 9. 9 + 2 = 11. 11 + 8 = 19!
   * Write the 9. Carry the 1.
2. The Long Tens Column: 1 + 1 = 2. 2 + 2 = 4. 4 + 1 = 5. 5 + 3 = 8!
3. Answer: 89!

🎯 The "Double Carry" Warning: When adding four numbers, your Ones column could easily add up to something huge, like 24! If that happens, you have to write the 4, and Carry a 2 to the Tens column! (Just add +2 instead of +1 down the tens side).

Try it

Build the skyscraper!

Instructions: Add down the massive columns. Check your work twice!

Problem 1:
   1 2
   2 4
   3 1
 + 1 2
--------
* Ones (no carrying needed here!): 2+4+1+2 = ___
* Tens: 1+2+3+1 = ___
* Answer: ___

Problem 2:
  (+1)
   2 5
   1 8
   2 2
 + 1 4
--------
* Ones: 5+8+2+4 = 19. (Write 9, carry 1!).
* Tens: ___
* Answer: ___

Problem 3:
   1 4
   1 4
   2 4
 + 2 4
--------
* Answer: ___

Problem 4 (Double Carry Warning!):
   1 8
   2 8
   3 8
 + 1 0
--------
* (Hint: 8+8+8 = 24! Carry a 2!).
* Answer: ___

Complete & Continue →