Which would you do in your head?

Hello there mathematicians, so we're a little bit curious.

When you look at these 6 problems here, which ones of these would you solve using a mental strategy, if any? And which ones would you prefer to solve using a written or digital strategy?

So in your notebook or with your classmates and your teacher, can you record which ones of those would you feel comfortable solving mentally, and which ones would you prefer to use a written or digital strategy?

Something that you could do, actually, is survey your classmates, and find out is there a problem, or are there problems, that everyone would use a mental strategy for? And also, is there a problem or problems that everyone would use a written or digital strategy for?

Over to you mathematicians and we'll be back together soon.

Welcome back mathematicians.

Let's have a look.

So we collected your thoughts and you might have collected some ideas from your classmates or family and friends too. We also asked some students and we colour coded their responses so the ones highlighted in pink are problems that everybody agreed they would use a mental strategy for. So let's have a look at those first.

These were the ones that said could confidently could use a mental strategy, and in this case I think it would be the most efficient way for them to solve the problem.

Yeah, so let's have a look at what they were thinking. They said for 1001 - 3. If you subtract 1 that gets you to 1000 and then subtract 2 gets you to 998.

And for 235 - 44, some of the students were saying, well, if you minus, inside of 44 is 35 and 9. So subtract 35 from 235 to get to the landmark of 200 and then 200 - 9 is 191.

And then for 98 plus something is 266, they said they would build up, so from 98 if you had two more, you get to the nearest 100. Then from 100 they know they just need 166 more. So that means that the missing addend is 168.

But there were also some problems with like, "Oh, my gosh, we think for this we would like to use a Calculator or a written strategy. So we thought we'd have a look at these two in particular and see whether there are some mental strategies we could also apply if we were more confident in working flexibly with numbers with decimals.

So let's have a look at 7 and 5 tenths + 15 hundredths + 6 and 5 tenths.

And the first thing that we noticed actually it was about the 5 tenths; that 7 and 5 tenths, and 6 and 5 tenths both had a 5 tenths, and we could join that together to make another whole, which would mean that we're rethinking of the number as 7 and 15 tenths and 7 whole more. Yeah, and then you could join the two sevens together to get 14. And then, add back on the 15 hundredths an you'd get 14 and 15 hundredths.

So, what looks like a problem where we thought, "I would use a written strategy or a digital strategy like a Calculator when actually we could rethink about this by using strategies that we know,like partitioning numbers and using known facts and renaming.

So, mathematicians, over to you now to see how you went with your classmates. Are there any of those problems that you could now rethink? And go, "Actually, let's have a look at, are there any of these that we could solve mentally that we thought, before, we wouldn't?

So over to you, mathematicians.

Have a lovely day.