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# Unit 2 learning overview

You can use this overview to inform your planning and help secure children's learning of the mathematics covered in the unit. It includes children reading and writing two-digit and three-digit numbers, partitioning two-digit numbers in different ways, recording calculations as addition and subtraction statements, using number bonds, and solving word problems.

Children build on their knowledge of reading and writing two-digit and three-digit numbers. They know that 200, for example, has a 0 in the 10s and units columns. They understand that when they write 265 the 0s are replaced: in the 10s column by 6, to give 60; and in the units column by 5, giving 265.

They use practical equipment such as 100-squares and arrow cards to develop and support their understanding. For example, they select arrow cards for the numbers 10, 50, 90 and explain why there is only one card for each of these two-digit numbers.

They partition two-digit numbers in different ways, for example:

• $25=20+5$
• $25=10+10+5$
• $25=10+9+6$
• $25=19+6$

They find missing numbers in calculations such as $37=30+\square +2$.

Based on their experience of counting objects, children estimate the number of objects in a set. For example, having counted how many counters fill a cup, they estimate the number of counters in a cup that is about half full. They discuss and compare estimates and explain how the estimate was reached.

Children count on from and back to any number in ones, including across tens and hundreds boundaries. They count in tens across hundreds boundaries, using equipment such as base-ten apparatus, coins or a calculator to secure their understanding. Children use their understanding of partitioning and place value to explain the effect on the digits of adding ten to or subtracting ten from a number. They explain that we can add or subtract nine to or from a two-digit number by adding or subtracting ten then adjusting. They illustrate why this works, for example using a 100-square or number line to demonstrate their understanding.

Children understand and use the term difference and find or describe the difference between two numbers practically. They count how many more cubes there are, say, in a tower of 15 cubes than a tower of 11 cubes to find the difference between 15 and 11. They find how much they need to count on from 29 to reach 34 to find the difference between 29 and 34. Children learn that finding the difference involves comparing two numbers and either counting on from the smaller number or subtracting the smaller number from the larger number. They demonstrate this on a number line. They record these calculations as addition or subtraction statements, for example:

$29+\square =34$ $34-29=\square$

Children identify how much to add to any two-digit number to reach the next multiple of ten, using their knowledge of number bonds to ten; for example, they solve $32+\square =40$. They find as many ways as possible to complete a missing-digit calculation such as $\square 1+\square =\square 0$, recording their results in a logical way and explaining the patterns and relationships in their results.

Children add or subtract multiples of ten by counting in tens. For example, they work out $84-30$ by counting back in 10s: 74, 64, 54. Children use a 100-square or jottings on an empty number line to support their method; they then visualise the numbers and dispense with the support. Children recognise patterns in examples such as $90-20=70$ and $9-2=7$ and use their knowledge of number bonds to remember and recall the sums and differences of multiples of ten.

Children solve word problems, using any one of the four operations. Given the problem of sharing 15 grapes equally among 3 people, for example, they identify an appropriate operation and record the solution as a number sentence. They use equipment, jottings, drawings or symbols to support their method. They record their work, describe their own method and compare it with others' methods.