Add a Multiple of 100 to a 3-Digit Number
š 100, 200, 300... Blast off the final dial! Adding massive "zero" numbers is the easiest trick in second grade.
Concept
We already learned how to jump by 100s. This is the exact same trick! šÆ **The "Hundreds Only" Trick:** **Example: 425 + 300 = ?** Because 300 ends in TWO zeros... the Tens and Ones places of your starting number are completely safe. They won't change! 1. **Cover up the Tens and Ones:** Just look at the Hundreds. 4 + 3 = 7. 2. **Put the 7 in the Hundreds place:** The answer will start with a 7. 3. **Bring back the frozen numbers!** The "25" drops right back in where it was. So, **425 + 300 = 725**! It looks like a giant, scary problem. But you only solved "4 + 3 = 7".
Try it
Turn the Hundreds dial! **Instructions:** Add the multiples of 100 by changing ONLY the Hundreds digit! Keep the back two digits frozen! **Problem 1: 512 + 200 = ?** * Just add the hundreds! (5 + 2 = ___) * Keep the "12" frozen! * Answer: ___ **Problem 2: 684 + 100 = ?** * Answer: ___ **Problem 3: 299 + 400 = ?** * Answer: ___ **Problem 4: 105 + 500 = ?** * Answer: ___ **Problem 5: 350 + 600 = ?** * Answer: ___