Maths homework in Y4, help with addition homework please

[Jodee]

DS has addition homework where he has to show all his working out. this is fine for the following:

56 + 45 =

DS knew that it had to be broken down into columns of units and tens and each added up separately to get the answer.

He doesn't know how to work out:

45 + __ = 90 (and neither do I - obviously I know the mental arithmetic to get the answer but not the method used!)

it looks like the answer would be achieved by subtraction, but he is supposed to be doing addition - can anyone tell me the method please (otherwise I will ask teacher tomorrow). Thank you!

how aobut a number line?

Ask him if they use an empty number line in school....this is a common method to solve a 'missing number' calculation. It's called 'finding the difference'.

Put 45 at one end of a horizontal line and 90 at the other end. Then hop from 45 to 50 (5) and then from 50 to 90 (40) either as one jump of 40 or four jumps of 10. Then add the total of the jumps.

Rather convoluted to explain without the number line...hope this makes sense.

Cross posted!

yes infin - but yours was infinitely better than mine - more explanatory

56
45+

6+5=11

1 stays under the 5

other 1 gets added to the 5 and the 4 to make 10. This is written in front of the other 1 to make 101

90
45-

0-5 cant be done

Change 9 to an 8 and turn the 0 into a 10

10-5=5 (written under the 5)

then 8-4=4(written under the 4)

answer is 45

Make sense?

Tis is how i did it at school. (20 years ago!!)

xx

but are year 4's learnign that method girly. yet?
i would leave it - otherwise he might be confused if your method is unknown to him.

Erm,

Im not sure,

Im in Scotland, not sure how old year 4 is?

That the way we learned when we were about 7/8
but that was in 1987!

xx

well mine dont learn that method til year 6, and thus year 4, age 8 to 9, is quite difficult in maths - in my experience

my dh did your method girly with my dd, in year 4, and i told him off - on the other hand i didnt know any other method either, aside from number line

Ah I see,

Oh well, maybe someone with kids in that area/ age may have another way.

Ive never been able to sus the English school ages/years out.

xx

and me too to scotland

thanks for posts - on googling, it would appear that the way ds (aged 8.9) worked it out for the first sum was correct, and alongside this was what I presume to be the number line (I couldn't imagine this in my head, I needed a picture!), and I could work out the second sum with the missing figure from there - I'll do an example for DS and see if that reminds him of how he was taught this week (he may well have been daydreaming about Star Wars at the time!)

Thank you!

I think you add horizontally not vertically so you would break it down into a longer number sum. E.G. 56+45=50+40+6+5=90+11=101. Does this make any sense to you?!

Sorry just re-read the op and realise you know how to do this already.

Sorry just re-read the op and realise you know how to do this already.

FYI, this is the way DS has been taught to do a straightforward addition sum:

367+
185

12
140
400

552

SlartyBartFAST

xx

that's OK, Keevamum, I wanted to see if this was the usual teaching method!

Dd1 is year 4 and uses a number line for this type of equation with 45 at one end and 90 at the the other as ifin describes