Making ten
Why ten is the number worth knowing by heart, and how it makes adding easier.
The ten frame shows you
A ten frame is two rows of five. Put counters in and the empty spaces tell you what is missing, without any counting at all.
Six counters in. Look at the gaps: four. So six and four make ten.
The pairs that make ten
There are only six pairs to learn. Six.
Once you know them, a great deal of adding becomes easy, because you can always look for a ten first.
Bridging to ten
Nine and three is hard to see. Ten and two is easy. So turn the first one into the second.
Move one counter across. The nine becomes ten, and the three becomes two. Nothing has been added or taken away — the counters were only shuffled — so the answer is the same.
Ten and two is twelve.
Why ten and not some other number
Ten is worth this trouble because of how we write numbers. Twelve is ten and two. Thirty-four is three tens and four.
Every time you make a ten, you have made a piece that the number system already knows how to hold. That is why looking for tens is the first thing to try.
Bridging, shown on the frame
Eight plus five is hard to see all at once. Ten plus three is not.
So move two of the five across to finish the ten. The five splits into two and three: the two completes the frame, and the three is left over. Ten and three is thirteen.
Nothing has been added or taken away. The same thirteen counters are sitting in a shape that is easier to read.
It works for taking away too
Thirteen take away five is the same trick run backwards. Take three first to get back to ten, then take the remaining two from the ten, which leaves eight.
Going down through ten is easier than counting back five times, and much easier than trying to hold the whole thing in your head.
The pairs that make ten do the work in both directions, which is why they are worth knowing by heart rather than working out each time.
Worked examples
A ten frame has 7 counters. How many more to fill it?
Do not count the counters. Count the spaces. The top row is full, and the bottom row has two in it, so three squares are empty.
Answer: 3
What is 8 + 5?
Eight wants two more to become ten. Take two from the five and give them to the eight. Now it is ten and three, which is thirteen.
Answer: 13
What is 6 + 7?
Either one can be the one you build up. Six needs four to reach ten, so take four from the seven: that leaves three. Ten and three is thirteen. Building the seven up instead gives the same answer: seven needs three, six has three to spare, and ten and three is thirteen again.
Answer: 13
Ravi has 4 marbles. How many more does he need to have 10?
This is one of the six pairs. Four and six make ten, so he needs six more. If you cannot remember it, picture a ten frame with four counters in and count the gaps.
Answer: 6
What is 9 + 6?
Nine needs one more to make ten, so split the six into one and five. Ten and five is fifteen.
Answer: 15
What is 15 − 7?
Take five first to get down to ten. That leaves two more to take, and ten take two is eight.
Answer: 8
Why is 7 + 8 easier once you know 7 + 3 = 10?
The eight splits into three and five. The three finishes the ten, and the five is left over, giving fifteen.
Answer: Because the 8 splits into 3 and 5
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