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To ask you to help me to help dd with maths homework?

(14 Posts)
ABunchOfFuckingPidgeys Thu 15-Sep-16 17:48:39

Dd is y7 and has brought maths homework home today, it's due back in tomorrow. Out of the 20 questions she's struggling with four as it's something she's not done much of at primary and has asked me to help her.
I'm in a bit of a panic because I'm really stupid with maths, I was hoping someone could explain how to work this out or point to a website that will explain without confusing me, or one dd could use herself?

One of them is

Simplify 9a + 2b - 8a - 3b

And another is

Expand 3(1+11x)

The other two sums are the same but with different figures. I feel stupid at not knowing how to do this and am prepared for everyone an AIBU to laugh or take the piss. My maths skill involve knowing how much money I don't have.blush

vickibee Thu 15-Sep-16 17:52:23

Add the a's together then the b'/ so answer is a-b

3x1 is 3 and 3 x 11x is 33x so answer is 3 plus 33x
Multiply each number in brackets by number outside

MrsWinklepicker Thu 15-Sep-16 17:53:34

Right, look at the first expression, separate the elements that have "a"'ve got 9a - 8a which leaves you with 1a (which we just call a if there's only 1). Then the "b" elements... 2b - 3b...which leaves -1b or just -b. So we can simplify the expression to a - b

OurBlanche Thu 15-Sep-16 17:56:33

As vicki said:

Simplify 9a + 2b - 8a - 3b =

As = 9 - 8 = 1A
Bs = 2-3 = -1B
= A-B

And don't feel bad about finding it hard, as non maths teacher adults we don't tend to think about maths as sums, we just use it to work out day to day stuff.

Expand 3(1+11x)

3 x 1 = 3
3 x 11x = 33x
= 3 +33x

TeaStory Thu 15-Sep-16 17:57:02

To simplify, gather like terms together - all the "a"s, all the "b"s.

9a + 2b - 8a - 3b


9a - 8a + 2b - 3b

Now you can tidy up.

9a - 8a = 1a
2b - 3b = -1b
(Think of the "a"s and "b"s as objects, like apples and oranges, if it helps).

So the answer is 1a - 1b

Correct notation gives the answer

a - b


Expand 3(1+11x)

This means you multiply 3 by each of the bits inside the brackets. I'll use a star for the multiply symbol so we don't get mixed up with "x" the letter.

(3*1) + (3*11x)

= (3) + (33x)
= 3 + 33x

JamieFraserskneewarmer Thu 15-Sep-16 17:57:04

OK - so I would start by grouping the as and the bs together so you end up with 9a-8a+2b-3b. Then solve each bit independently so 9a-8a=1a (or a) then 2b-3b= -1b (or -b). Put them together and you end up with a-b.

On the expand one, the bracket tells you that the things inside it are to be multiplied by the number outside so 3x1 = 3 and 1x11x = 33x so you end up with 3+33x

The bbc bite size site is really useful for things like this bitesize

Jaynesworld Thu 15-Sep-16 17:58:09

For the last one "To expand a bracket, multiply everything inside the bracket by the number outside" so I think it's 3 X 1 + 3 X 11x
I'll try and figure out the first one too, it's been ages since I've done maths.

MrsWinklepicker Thu 15-Sep-16 17:58:47

The second expression means 3 x (1+11x) so you multiply each item in the brackets and add them it becomes (3 x 1) + (3 x 11x) which becomes 3 + 33x....if it was 3(1 - 11x) then it would be 3 - 33x iyswim.

MrsWinklepicker Thu 15-Sep-16 18:01:42

I think the important thing is not to panic and try to approach in a logical way...

ABunchOfFuckingPidgeys Thu 15-Sep-16 18:15:59

Thank you so so much everyone.

So the other simplify question is

9a + 5b + 7a + 8b

Would be

16a + 13b

I have a feeling I'm missing another step?

Her other expand question is

Expand 5(3-11x)


5x11x= 55x

Answer is

She's not tried them yet, just wanted to double check I'm on the right kind of lines. Thank you so much again, it really helps.

olderthanyouthink Thu 15-Sep-16 18:27:04

Your answers look correct to me

(I don't remember doing this stuff that early in secondary school hmm)

OutDamnedWind Thu 15-Sep-16 18:28:57

Yea, both those are right smile

ForFiveMinutes Thu 15-Sep-16 18:38:53

Yes you are right and I set this very same homework (from a subscription website) to my year 7's last week!

ABunchOfFuckingPidgeys Thu 15-Sep-16 19:10:56

Thank you so much again, I explained the way everyone mentioned here and she's managed to do them herself. It's not often that she brings her maths to me to help because she knows I'm not too great at it and I'm really chuffed that I managed to understand it myself too.

I had a horrible maths teacher and he once made me stand in front of the whole class while he screamed at me for going ahead of the class in our text books and that I'd created more marking for him and to explain to the class why I thought I'd be smart enough to do an extra page since I got most of the extra questions wrong. Teachers in previous years encouraged doing a bit extra if we had time and felt able and I loved maths until then, I had a whole year to go and hated maths as he'd make me anxious about getting it wrong as he'd humiliate people who got stuff wrong. The wanker.

forfiveminutes dds sheet is from and to be honest I probably calling do half of them, just as well she doesn't get her maths skills from me.

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