This week we have focused on choosing a mental strategy to help solve two digit addition and subtraction. We used this flow chart to help us choose which method would be the quickest or easiest.
Examples of questions are below:
- group the tens and ones and then add them together (12 + 15 = 10 + 10 + 2 + 5)
- count on from the smaller number (25 – 21 -> jumping on in ones from 21 is 22, 23, 24, 25 a total of 4 jumps)
- count back using your fingers (35 – 4)
- count back using tens and ones – we decided that this was the hardest to do – (35 – 12 -> 35 – 10 = 25 then 25 – 2 = 23)