# Practice Addition and subtraction strategies for 1-10 facts.

In first and second grade children learn how to mentally add and subtract 1-10 numbers and need to understand the strategies:

• Count up
• Count down
• Double Partner
• Double neighbour
• Ten's partner
• Make ten
In this practice students should choose an optimal strategy first and than solve the problem.

### Count up

Counting up is a simple way to add a small quantity to a larger quantity.
Example: for 14 + 2, a child might count up two saying 15, 16.

Although counting up can be used to add larger numbers together, it is time consuming and not as efficient as other strategies. We encourage counting up for adding small quantities like 1, 2, or 3 to an amount.

### Double Partner

Double partner facts are relatively easy to learn and become powerful anchors for other addition facts. Students should learn and identify patterns below.

 1 + 1 = 2 6 + 6 = 12 2 + 2 = 4 7 + 7 = 14 3 + 3 = 6 8 + 8 = 16 4 + 4 = 8 9 + 9 = 18 5 + 5 = 10

### Double neighbour

Double neighbors are also called “doubles-plus-one”. The strategy is to double the smaller addend and add one or two more.

If you know 6 + 6 is 12, then 6 + 7 is just 6 + 6 + 1 = 13.
If you know 5 + 5 is 10, then 6 + 5 is just 5 + 1 + 5 = 11.

### Ten's partner

Ten's partners are combinations of numbers that equal 10. Understanding how numbers relate to 10 (ex: 8 is two away from 10) is critical for fluent computation.

 0 + 10 = 10 3 + 7 = 10 1 + 9 = 10 4 + 6 = 10 2 + 8 = 10 5 + 5 = 10

### Make ten

Make ten is an important strategy because it is easy to add a number to 10 (or to a multiple of 10). This is an important feature of our base-10 number system.

For 6 + 9, think 5 + 10 => split the 6 to make the problem 5 + 1 + 9 = 5 + 10
For 6 + 8, think 4 + 10 => split the 6 to make the problem 4 + 2 + 8 = 4 + 10

## Subtraction strategies

### Count down

Counting down is a simple way to subtract a small quantity from a larger quantity.
Example: for 14 - 2, a child might count down two saying 13, 12.

Although counting down can be used to subtract larger numbers, it is time consuming and not as efficient as other strategies. We encourage counting down for subtract small quantities like 1, 2, or 3 from an amount.

### Double Partner

Double Partner strategy: If you know the sums of 9+9, 8+8, 7+7, and 6+6, then you know the differences for:

 18 – 9 = 9 10 – 5 = 5 16 – 8 = 8 8 – 4 = 4 14 – 7 = 7 6 – 3 = 3 12 – 6 = 6 4 - 2 = 2

### Double neighbour

Double neighbour strategy: By knowing double facts, you can also solve “close” facts:

16 – 8 = 8, so 17 – 8 = 9
14 – 7 = 7, so 13 – 7 = 6

### Ten's partner

Ten's partner strategy: If you know that 9+1, 8+2, 7+3, 6+4, and 5+5 all equal 10, then apply this knowledge to subtraction facts:

 10 - 9 = 1 10 - 5 = 5 10 - 8 = 2 10 - 4 = 6 10 - 7 = 3 10 - 3 = 7 10 - 6 = 4 10 - 2 = 8 10 - 1 = 9

### Make ten

Make ten strategy: Convert a minus 9 to minus 10, and then add 1 back:
For 15 – 9 = ?, think 15 – 10 + 1 = 6

Convert a minus 8 to a minus 10, and then add 2 back:
For 13 – 8 = ?, think 13 – 10 + 2 = 5

## Progress report

The report shows learning progress in percentage (0% - not learned, 100% - learned perfectly).
There are three levels of the report.

### Short report

Subtraction strategy: 54%

### Normal report

1-10 addition, subtraction strategies learning progress:

 Counting up(down) 87% Double partner 26% Double neighbour 27% Ten's partner 43% Make ten 87%

### Full report

Counting
Count up83% Count down90%
Double partner
1+120% 2-140%
2+20% 4-20%
3+30% 6-380%
4+460% 8-436%
5+5100% 10-580%
6+620% 12-60%
7+720% 14-70%
8+80% 16-820%
9+920% 18-920%
10+100% 20-100%
Double neighbour
1+0, 1+20% 1-1, 3-120%
2+1, 2+310% 3-2, 5-220%
3+2, 3+40% 5-3, 7-310%
4+3, 4+520% 7-4, 9-430%
5+4, 5+610% 9-5, 11-550%
6+5, 6+730% 11-6, 13-679%
7+6, 7+832% 13-7, 15-740%
8+7, 8+910% 15-8, 17-860%
9+8, 9+1048% 17-9, 19-90%
10+9, 10+1150% 19-10, 21-1010%
Ten's partner
1+960% 10-10%
2+890% 10-20%
3+70% 10-320%
4+660% 10-420%
5+5100% 10-580%
6+420% 10-660%
7+3100% 10-756%
8+20% 10-860%
9+140% 10-90%
Make ten
XX+9100% XX-987%
XX+880% XX-880%