Add FOUR 2-Digit Numbers
š¢ Build the skyscraper! Three numbers was a mountain, but four numbers is a skyscraper. Don't speed, or the tower will fall!
Concept
Okay, things are getting serious. Stacking FOUR two-digit numbers requires ultimate concentration. šÆ **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**! šÆ **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: ___