Use Ten to Subtract
🦸♂️ Ten is your superpower! When you have a tough subtraction problem in the teens, you can use the number 10 as a stepping stone to find the answer fast.
Do this: Read the concept below, then try the quiz or activity.
Concept
Numbers like 15 or 16 can be tricky to subtract from directly. But every "teen" number has a hidden 10 inside it! We can use this to our advantage.
🎯 The "Step on 10" Strategy: Example: 15 - 8 = ? This is a hard fact. But let's break the 8 into two smaller steps. 1. Step 1: Get down to 10. To get from 15 down to 10, you have to subtract 5. 2. Step 2: Figure out what's left of the 8. We already subtracted 5. That means we still need to subtract 3 more (since 5 + 3 = 8). 3. Step 3: Subtract from 10. Now just do 10 - 3. What is the answer? 7!
So, 15 - 8 = 7. We used 10 as a resting spot halfway through the jump!
Try it
Let's practice the "Step on 10" strategy!
Instructions: Break the second number into two parts. Use the first part to get down to 10!
Problem 1: 14 - 6 = ? * Step 1: Take away 4 to get to 10. (14 - 4 = 10) * Step 2: The 6 was made of 4 and 2. We still need to subtract 2. * Step 3: 10 - 2 = ___ * Answer: 14 - 6 = ___
Problem 2: 13 - 5 = ? * To get from 13 down to 10, take away ___. * We still need to take away ___ more. * 10 - ___ = ___ * Answer: 13 - 5 = ___
Problem 3: 16 - 7 = ? * Answer: ___
Problem 4: 15 - 9 = ? * Answer: ___