Subtracting 8
🕷️ An octopus has 8 legs. If we subtract them all, how many are left? Let's use our tricks on number 8!
Do this: Read the concept below, then try the quiz or activity.
Concept
8 is a big number to take away. The fastest way to subtract 8 is to Count On up to the 10!
🎯 The "Count On from 8" Strategy: Example: 13 - 8 = ? 1. 8 is super close to 10! It's only 2 steps away. 2. The number 13 is 3 steps past 10. 3. Just add your steps together! 2 + 3 = 5. So, 13 - 8 = 5.
Any time you subtract 8 from a teen number, the answer is just the "ones" digit plus 2! * 14 - 8 = 4 + 2 = 6. * 17 - 8 = 7 + 2 = 9.
Try it
Let's try the plus-two rule!
Instructions: Subtract 8 by adding 2 to the ones digit (or use your favorite strategy).
Problem 1: 15 - 8 = ? * Add 2 to the 5. (2 + 5 = 7) * Answer: 15 - 8 = ___
Problem 2: 12 - 8 = ? * Add 2 to the 2. * Answer: ___
Problem 3: 16 - 8 = ? * (Wait! Is this a double?) * Answer: ___
Problem 4: 11 - 8 = ? * Answer: ___