Mixed Practice: Adding Groups of 10 or 100
π The Dial Switcheroo! Sometimes you change the Hundreds dial. Sometimes you change the Tens dial. You have to check the zeros to know which dial to spin!
Do this: Read the concept below, then try the quiz or activity.
Concept
Okay, the trick is easy. But now they are going to mix up the problems!
π― The "Check the Zeros" Strategy: Before you add, look at the number you are adding. How many zeros does it have?
* ONE Zero (Example: 40): This is a Ten! Only turn the TENS dial! The Hundreds and Ones stay frozen! * 625 + 40 = 665. (Only the middle 2 changed to a 6). * TWO Zeros (Example: 300): This is a Hundred! Only turn the HUNDREDS dial! * 625 + 300 = 925. (Only the 6 changed to a 9).
If you accidentally add 40 to the Hundreds place, your answer will be completely ruined!
Try it
Spin the correct dial!
Instructions: Look at the zeros! Are you spinning the middle Tens dial, or the far-left Hundreds dial?
Round 1: Tens Dials! (One Zero) 1. 345 + 20 = ___ (Only change the middle!) 2. 819 + 60 = ___
Round 2: Hundreds Dials! (Two Zeros) 3. 542 + 300 = ___ (Only change the front!) 4. 199 + 700 = ___
Round 3: The Blender! (Mixed Up) 5. 650 + 200 = ___ 6. 431 + 50 = ___ 7. 222 + 400 = ___ 8. 518 + 70 = ___