Pupils need to be able to identify or place two-digit numbers on marked number lines. They should use efficient strategies and appropriate reasoning, including working backwards from a multiple of 10.
“a is 36 because it is one more than the midpoint of 35.”
“b is 79 because it is one less than 80.”
Pupils should also be able to estimate the value or position of two-digit numbers on unmarked numbers lines, using appropriate proportional reasoning, rather than counting on from a start point or back from an end point. For example, here pupils should reason: “60 is about here on the number line because it’s just over half way”.
To prepare for future work on rounding, pupils should also learn to identify which 2 multiples of 10 a given two-digit number is between.