Crossing the tens boundary counting forwards and backwards | Maths

Starter quiz

When does the pattern of counting change when counting backwards?
- when you cross the tens boundary ✓
- when you count the forties
I'm thinking of a number. It is in the fifties and ends in 6. What is my number?
- 65
- 56 ✓
- 506
Sort these numbers in the order you would say them if counting forwards.
- 1
  
  ⇔
  
  5 tens 7
- 2
  
  ⇔
  
  5 tens 8
- 3
  
  ⇔
  
  5 tens 9
- 4
  
  ⇔
  
  6 tens
Lucas counts backwards from the number 76. What numbers will he say next?
- 75, 74, 73 ✓
- 77, 78, 79
When counting forwards from 34, which of these numbers will you say?
- 29
- 43 ✓
- 34
When counting backwards from 34, which of these numbers will you say?
- 29 ✓
- 35
- 43

Aisha starts counting at 49 and finishes at 54. She must be counting __________.
- forwards ✓
- backwards
When counting backwards from 60, which of these numbers would come first in the count?
- 37
- 47
- 57 ✓
Lucas is counting forwards from a number ending in 9. What was the number he started at?
- 29
- 49
- 39 ✓
Aisha is counting backwards from a decade number. What was the decade number she started at?
- 60
- 50
- 70 ✓
Lucas is counting forwards from 45. What is the next decade number he will say?
- 40
- 50 ✓
- 60
Aisha is counting backwards from 45. What is the next decade number she will say?
- 40 ✓
- 50
- 30

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The numbers from 0 to 100 have patterns that can help us to count forwards and backwards across the tens boundary.
They are arranged differently on a number track and on a one hundred square.
We can count the numbers in two ways.
When a number ends in a 9, it is always followed by a decade number when counting in ones.

Confusion around the numbers which cross the tens boundary, e.g. 39, 40 may say 39, 30

Make errors for the children to discuss; encourage them to explain and correct mistakes.

Cross the tens boundary - The point at which the counting moves from one decade into another.
Forwards - When you count forwards the number become greater.
Backwards - When you count backwards the number become less.