1. Mental Math 101: Parent Tips Carla Kolada—Numeracy Lead

2. Why is Mental Math Important? Estimating total cost Calculating tax, discounts, tips Doubling/halving a recipe Splitting cab fare Buying fabric, lumber, paint Telling time

3. Believe it or not, we use Mental Math all the time!

4. O Mental Math is not about using tricks that don’t make sense, but instead, it’s about being able to work with numbers in a way that makes computations easier. O In order to do that, children (and adults) need to develop excellent number sense. O If you understand WHY a strategy works, then it’s much more likely that you’ll be able to remember it. Then, you can use it effectively and in a variety of situations.

5. Let’s try it out! 47 + 34 Hmm…How could I do this in my head?

6. We could try this: 47 + 34= 40 + 30 7 + 4 70 + 11 = 81

7. Or it might look like this: 47 + 34

8. Perhaps, like this: 47 + 34

9. Or maybe even like this: 47 57 67 77 80 81 +10 +10 +10 +3 +1 47 + 34 If I count on from 47, that makes sense, too!

10. How about this? 52 x 4 Or, maybe I could multiply it by 2 first. What if I thought about 52 as 50 and 2 more?

11. We don’t all think the same way, so it’s okay to use different strategies.

12. Front-End Addition: O Start at the left – not always in the ‘ones’ place: 1 489 + 237 1 000 + 600 + 110 + 16 = 1 726 (less chance of calculation error than re-grouping)

13. Compatible Numbers Which numbers “go together” to make it easier to do the Math in my head? 25 + 18 + 75 These are also called “nice numbers” or “friendly numbers” ?

14. Compensation – sometimes called the ‘Robin Hood’ strategy O When adding, take from one and give to the other. 398+ 17 Why not take 2 from the 17 and give it to 398? It becomes 400 + 15 much easier!

15. Compensation: Constant Difference 178 – 37 You could subtract 7 from each number – keeping the ‘difference’ between the two numbers the same 171 – 30 is easier to calculate! You could also have added 3 to each…making it 181 – 40 Same answer…because you kept the ‘difference’ between those two numbers the same.

16. Multiplying Tips How can I use parts of numbers to multiply faster…and easier? Split them up: 17 x 5 is the same as 10 x 5 plus 7 x 5 50 + 35 = 85 Double - Double to help with groups of 4 7 x 4 = double 7 (14)….then double 14 (28) Double Half --When multiplying, double one factor and half the other factor. Would you rather multiply 5 x 18? Or 10 x 9?

17. Let’s Practice!

19. And, when you feel like calling for reinforcements, remember, think about what would make sense!