In Maths this week, we have began to add and subtract numbers in Year 3, starting with adding and subtracting 1s and 10s from 3 digit numbers, followed by adding and subtracting 1s across multiples of ten.
This involved adding single digit numbers which leave an answer greater than the next multiple of ten (for example, 156 + 8) and subtracting single digit numbers which leave an answer less than the previous multiple of ten (for example 183 – 7).
To begin with we used base 10 equipment so the children could see for themselves why we need to exchange 1 ten for ten ones when we add and subtract. They could not physically take away more ones than they had when they had to subtract and they could not keep more than ten 1s in the 1s column when they had to add, so they had to exchange one of their tens for ten 1s in order to carry out the calculations.
The children worked very well together in groups and once they were secure with using the base 10 equipment to calculate, we moved on to doing similar calculations on whiteboards. They had to draw squares for hundreds, lines for tens and small squares for 1s. If they were subtracting, they would rub out a ten and add ten small squares to help them. If they were adding, they would rub out ten 1s and add a ten to help them.
The children did very well with the whiteboard work and were able to apply their understanding to solving problems (which got progressively more and more tricky) presented by our Maths scheme of work, Power Maths. The next step is to add and subtract multiples of 10 across multiples of 100!
