Mixed Practice: 3-Digit Subtraction
π The Ultimate Decider. Look at the problem. Should you use a Trick? Or should you line it up and do the hard work?
Do this: Read the concept below, then try the quiz or activity.
Concept
Do not become a robot that just blindly stacks numbers.
π― The Assassin's Guide: Look at the bad guy (the number you are taking away). 1. Is it a perfect hundred? ( - 200). Use the Dial Trick! 2. Is it almost a hundred? ( - 199). Use the Steal/Return Trick! 3. Are the ones all zeroes? ( - 30). Use the Dial Trick! 4. Does it look ugly? ( - 157). STACK IT VERTICALLY IMMEDIATELY.
If you don't pick your weapon wisely, you will take 10 minutes to finish a 1-minute test.
Try it
Pick your weapon!
Instructions: Look at the bad guy number. Pick the best trick.
Problem 1: 582 - 300 = ? * (Trick: Just spin the hundreds dial backward! 5 - 3). * Answer: ___
Problem 2: 745 - 299 = ? * (Trick: Steal 300, Give 1 back!). * Answer: ___
Problem 3: 864 - 521 = ? * (Gross numbers! STACK THEM on scratch paper!). 864 - 521 -------- * Answer: ___
Problem 4: 928 - 98 = ? * (Hint: Steal 100, give 2 back!) * Answer: ___