Easy maths help for stupid mum��

[commonmisconception]

Hi all...help appreciated on this maths problem please!! (Don't judge me!!)

I am really trying to swat up on maths to help DD with homework (year 5) and just when I think I have something cracked, she comes home with yet another problem that has me running round in circles!!

The question is 304 - 279 and I just cannot figure out how to solve it using the column method and 'borrowing' from the tens/hundreds columns. DD came up with 75, and I keep ending up with 35 (in the tens/units section - that's as far as I get before starting again.)

I know by checking on the calculator that the answer is 25 - so what do I do to get there??.

Huge thanks and in advance (and a for me!!)

304
279

you can't take 9 from 4 so you need to borrow from the tens. there aren't any tens so you borrow ten tens from the hundreds column. so cross out the 3 and write a small 2. then put a 10 above the 0. now you can borrow a ten from the tens column, so cross out the 10 and put a 9 and put a 1 next to the 4 to make 14. so now it's 14-9=5 in the units column. 9-7=2 in the tens column, and 2-2=0 in the hundred column. so answer is 25. hope this makes sense.

You are having a problem with the abstract nature of the problem, until you understand the concrete part, the theory won't make sense.
I'd use money.
Draw yourself three colums on a sheet of A4 and label them HTU.
Now put three £1 coins in the H column and 4 pennies in the units.
You need to pay for something worth £2.79 and the answer is the amount of change.
What do you need to do?
Which coins do you need to exchange?

304-279

You can't borrow from zero, so you just borrow from the next column over. So, you have to borrow from the three. Three becomes two, you put the one in front of the zero to make ten. You can then borrow one from the ten to become nine and add the one to the four to make fourteen.

You then have 14-9 to give 5.
9-7 to give 2
2-2 to give 0

That gives you 25.

Thanks everyone! Problem solved - I had trouble with the zero and instead of changing it to 9 I was leaving it as 10, giving me 3 (hope that makes sense!)

Thanks again - the tension headache has lifted!!

At the risk of flogging a dead horse, and to get your own head round the numbers, you could look at it another way so you understand the logic rather than just doing the technique.

As the sum is 304 - 279, imagine the numbers sitting on a line with 300 sitting in the middle. 304-300 is 4. 300-279 is 21. (Or 300-280 is 20 and 280-279 is 1.) So total difference between them is 25.

And I'd suggest you get your own copy of DD's textbook if you can and work through it slowly, a week or so in advance so nothing stumps you.

You can also do it as what is the difference between them?

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