Addition Facts – Strategies for Thinking
Strategy
+ 1/+ 2
Foundation Facts
+0
+ 10
Doubles
Building on the Foundation
Making
Ten
Using
Tens
Description
Examples
Students build on their understanding
of counting to add 1 or 2 more (and 1
or 2 less). Count on to add one or two
to any number.
Students should think about what
happens when they add or subtract
nothing from a number.
Adding 10 to a single-digit number
results in a 2-digit sum. Students
practice adding 10 in order to build
understanding and automaticity that
will be needed later with the “using
tens” strategy.
Students explore the concept of
doubling and what it means to add 2
groups of equal size.
Because 10 is foundational in our
number system, students explore the
different ways in which 2 addends
result in a sum of 10. This knowledge
becomes critical as they later explore
using tens to find unknown facts.
When students know combinations of
addends that have a sum of 10, they
use their understanding of the
flexibility of numbers to find ways to
break apart addends to create simpler
facts by using tens.
5+1=?
Think: I need to know one more than 5, so I
can count one number after 5 - 5, 6.
Students’ use doubles facts to find
unknown facts that are near-doubles.
Use when the difference between the
addends is 1 or 2.
Using
Doubles
3+0=?
Think: I am adding nothing to the number, so
it is still 3.
7 + 10 = ?
Think: I’m adding one group of ten to 7 ones,
so I add 1 ten (in the tens place) and the ones
stay the same, so 17.
5+5=?
Think: I just have to double the number, and
double 5 is 10
4 + ? = 10
Think: If I already have 4, I need to know how
many more will make a group of 10. I know 4
and 6 make ten, so 6 is the missing number.
9+7=?
Think: I can take one from the 7 (which leaves
6) to make the 9 into a 10. I know 10 + 6 = 16.
8+6=?
Think: I can use two from the 6 to make the 8
into a 10. I can take the 4 left from the 6, and
add 4 + 10 = 14.
4+5=?
Think: I know that 4 + 4 = 8, and 5 is one more
than 4, so I could add 4 + 4 + 1 = 9.
9+8=?
Think: I know that 9 + 9 = 18, and 8 is 1 less
than 9, so if I take one away from 18, I get 17.
9 + 9 – 1 = 17
7+5=?
Think: I can take one from the 7 and add it to
the 5, so now both groups are 6. I know that
6 + 6 = 12.
Adapted from: Mastering the Basic Math Facts in Addition and Subtraction, 2011, Susan O’Connell and John SanGiovanni