One, and one more
Here is 1 square on its own. Put 1 more square beside it. Now there is the square you had and the square you added.
This is written 1 + 1, and it is read "one plus one". The + sign means put together: take what is on the left of the sign and what is on the right, and join them into one group.
1 square, and 1 more square beside it: 1 + 1.
Push them together and count
Push the two squares together and count them, touching each square once: 1, 2. The last number you say is how many there are, so there are 2 squares.
So 1 + 1 = 2. The = sign is read "equals", and it means both sides are the same amount: 1 square and 1 more square is the same as 2 squares.
1 + 1: two piles, not yet one group to count
Push the two piles together
Pushed together, the two squares make one group, and counting it gives 1, 2: 1 + 1 = 2.
Any two piles
Adding any two piles works the same way. For 3 + 2, make a pile of 3 squares and a pile of 2 squares. Push the piles together, then count every square: 1, 2, 3, 4, 5. So 3 + 2 = 5.
Two slips give the wrong total. Touching one square twice counts it twice, and the total comes out one too many: 6 instead of 5. Stopping before the last square leaves one out, and the total comes out one too few: 4 instead of 5. Touch each square once, and count right to the end.
3 + 2: two piles, not yet one group to count
Push the two piles together
A pile of 3 squares and a pile of 2 squares. Pushed together they make one group, counted 1, 2, 3, 4, 5: 3 + 2 = 5.
One more is the next number
To add 1, there is no need to count everything again. The numbers always come in the same order when you count, so adding 1 more moves you on to the next number. 7 + 1 is the number after 7, which is 8.
Worked example: Ducks Counted One by One, Then One More Duck
Question There are 7 ducks on a pond. Mei touches each duck once as she counts. (a) What is the last number Mei says? (b) One more duck comes to the pond. How many ducks are there now?
1.Draw one counter for each duck, all in a row.
One counter is one duck. There are 7 counters in a row. 2.Touch each counter once and count: 1, 2, 3, 4, 5, 6, 7.
Touch each counter once and say one number for each: 1, 2, 3, 4, 5, 6, 7. 3.(a) The last number Mei says is 7. There are 7 ducks.
(a) The last number Mei says is 7. There are 7 ducks. 4.(b) Draw one more counter. The number after 7 is 8, so 7 + 1 = 8. There are 8 ducks now.
(b) One more duck comes. The number after 7 is 8, so 7 + 1 = 8 ducks.
Answer: (a) 7; (b) 8 ducks
Common mistakes
- Touching one duck two times and saying 8 in part (a). Each duck gets one number only, so touch each duck once.
- Counting all the ducks again from 1 in part (b) and losing your place. You know there are 7, so one more is the next number, 8.