Complete the Addition Sentence (Algebra!)
š§© The Missing Piece! You know the start, you know the total. Now use backwards math to find what's missing in the middle!
Concept
This is Algebra! But instead of the letter "X", it's just a blank space. šÆ **The "Opposite math" Rule:** **Problem: 325 + _____ = 850** If you have to add two numbers to get a total, then the difference between the Total and the Start is perfectly equal to the missing piece! 1. Take the Total (the biggest number): **850**. 2. **SUBTRACT** the piece you already know: **325**. 3. Do the math! (850 - 325). 8 5 0 - 3 2 5 --------- (Borrow from the 5, make 10. 10 - 5 = 5. Tens: 4-2=2. Hundreds: 8-3=5.) 4. **Answer: 525!** Let's check it! 325 + 525 = 850. It works perfectly.
Try it
Find the missing puzzle piece! **Instructions:** Take the Total, subtracting the piece you know! **Problem 1: 400 + _____ = 900** * Total: 900. Piece: 400. * Wait! Do you even need to stack this? Just use the dial! 9 - 4! * Answer: _____ **Problem 2: 152 + _____ = 684** * 684 - 152 = ? * Answer: _____ **Problem 3: _____ + 250 = 500** * Total: 500. Piece: 250. * Answer: _____ **Problem 4: 399 + _____ = 500** * (Hint: Just count up! What is 399 plus 1?) * Answer: _____