It is important that children have real confidence with adding any two digit numbers ( eg 42 and 58 ) and that they have a variety of strategies or approaches, depending on the numbers involved – sometimes it is easier to start with the tens, but not always. Constant practice, usually not on paper, of these tens and units additions will make larger mental addition much easier.
It is expected that children will usually use mental methods to add two digit numbers – NOT write the sum down. This might also be the case for adding HTU and TU.
For example: 125 + 36
Start with the hundreds and tens.
120 and 30 make 150. (Keep this number in the back of my head)
5 and 6 make 11.
Add this 11 to the 150 to make 161.
Easy!!!
These two maths worksheets focus on adding 2-digits to a 3 digit number.
Free Y5 maths worksheets: Mentally add larger numbers (pg 1)
Free Y5 maths worksheets: Mentally add larger numbers (pg 2)