Place value — tens and ones
Maths · Key Stage 1 · The School
Numbers are built from parts
The number 47 is not "four-seven" — it is 4 tens and 7 ones. 40 + 7 = 47. Every two-digit number splits this way. The LEFT digit counts tens; the RIGHT digit counts ones.
Comparing with place value
Which is bigger, 62 or 58? Check tens first: 6 tens beats 5 tens, so 62 is bigger — the ones never get a say unless the tens are equal. For 34 and 37, the tens tie (3 each), so compare ones: 7 beats 4, so 37 wins.
Building numbers
5 tens and 2 ones make 52. 7 tens and 0 ones make 70. Zero matters: it holds the ones place open so the 7 stays in the tens place.
The teen trap, and ordering three numbers
Thirteen SOUNDS like "three" and then "ten", which is exactly backwards from how it is written. 13 is 1 ten and 3 ones. The same trap sits in 14, 15, 16, 17, 18 and 19: sixteen is 1 ten and 6 ones, not 6 tens and 1 one. Build them to be sure — one ten stick and six single cubes. Now put 31, 13 and 30 in order. Tens first: 31 has 3 tens, 13 has 1 ten, 30 has 3 tens, so 13 is smallest. The other two tie on tens, so the ones decide: 1 beats 0. In order: 13, 30, 31.
Splitting to add
Place value is not only for reading numbers; it makes adding easier. For 34 + 23, split both: 30 + 20 = 50, and 4 + 3 = 7, so 57. Tens with tens, ones with ones. Try 45 + 12: 40 + 10 = 50, then 5 + 2 = 7, giving 57 again. The one thing to watch is what happens when the ones add past ten, because you have just made a new ten. 26 + 15 gives 30 + 11, and that 11 is 1 ten and 1 one, so the answer is 41. Writing 311 is the classic slip, and it comes from forgetting that the new ten has to move house.