Mental arithmetic should still be a vital part of lessons for children in Year 3 and we would like to highlight some of the main skills children need to have. These include:

• subtract by adjusting (e.g. taking 19 from a number by subtracting 20 and adding 1)
• subtract multiples of 10 from 3-digit numbers (e.g. 345 – 50 = )
• subtract single digits from 3-digit numbers (e.g. 345 – 8 = )
• mentally subtract any 2-digit numbers (e.g. 34 – 27)
• subtract multiples of 100 (e.g. 2,300 – 400 =)
• subtract by counting on (e.g. work out 301 – 297 by counting on from 297)
• understand subtraction as the inverse of addition and that answers from a subtraction can be checked by adding.

With these skills it is surprising how little written subtraction needs to be used in the real world, as most simple calculations can be done mentally. However, as the year goes on the focus shifts to written methods of subtraction. Watch out for children who don’t line up the digits correctly or who work from left to right, which doesn’t work once exchanges are introduced.

Don’t forget that as well as our main Subtraction category there are also plenty of subtracting activities in our Reasoning/Problem Solving category, including ‘bar modelling’ pages.