## Math Strategies

XTRA Math

Kathy Richardson

Improving Math Facts

1. Starting from the left, add up the numbers in the hundreds place.

2. Add up the numbers in the tens place.

3. Add up the numbers in the ones place.

4. Add up all the partial sums.

https://www.youtube.com/watch?v=mvdVjwbim6w#action=share

1. Look at the digit in the 1s place. If subtracting these digits results in a negative number then trade 1 ten for 10 ones.

2. Do the same for the 10s place, 100s place and so on.

3. Subtract in each column.

https://www.youtube.com/watch?v=sz2fy-9oCmA#action=share

Kathy Richardson

Improving Math Facts

**How to add using the partial sums method?**1. Starting from the left, add up the numbers in the hundreds place.

2. Add up the numbers in the tens place.

3. Add up the numbers in the ones place.

4. Add up all the partial sums.

https://www.youtube.com/watch?v=mvdVjwbim6w#action=share

**How to subtract using Trade-First Subtraction Algorithm?**1. Look at the digit in the 1s place. If subtracting these digits results in a negative number then trade 1 ten for 10 ones.

2. Do the same for the 10s place, 100s place and so on.

3. Subtract in each column.

https://www.youtube.com/watch?v=sz2fy-9oCmA#action=share