Is anyone able to help me with a maths problem?

[ILoveMyYuccaPlant]

Hi all DD has a maths test this Friday and I was helping her with revision last night. There is one task she was really stuck on and couldn't get her head around (nor could I, always been bad at maths unfortunately!). I've tried to encourage her to go to the maths revision group and ask teachers for help but she's a nightmare in this regard.

Anyway, this is the equation (?expression) she's struggling with, this was apparently covered on a day she was off school so is unsure what to do. I've put two of them on as they're slightly different to each other. Thanks to any fellow MNers who are mathematically minded and can help!

If p = 3, q = 8 and r = 4, evaluate the following:

q - 2p +5r

(r - p)squared - 2q

No

But I bumped it for you!

Haha thanks carriedout! My brain has never been able to compute many aspects of mathematics so I'm not a lot of use to DD here. I feel she's capable but lacks confidence and isn't great at asking for help if she needs it.

Ooo I'm not sure but maybe -

q - 2p + 5r =
8 - 2(3) + 5(4) =
8 - 6 + 20 = 22

(r-p)2 - 2(q) =
(4-3)2 - 2(8) =
1 - 16 = -15

I think? Sub the numbers in for the letters, deal with brackets first (which I thought meant the same as 2x8) then work through the equation?

Hello. What she needs to do is substitute the letter with the numbers. When a number is written before a letter (2p) this is shorthand for multiplication (2 x p).

So 2p = 2 x 3, because she’s been told p = 3.
5r is 5 x 4, because r = 4.

Then q - 2p + 5r is 8-6+20.

As long as she remembers the shorthand and the substitution, then she can move forward. If she is stuck or confused, she should work out each term (5r, r-p) separately and carefully.

She should have been told already to work out what’s inside brackets (r-p) before doing any squaring, adding, subtracting etc with numbers outside the brackets.

You just need to substitute in the given values for p, q and r. So the first one becomes 8-2×3+5×4=22, and the second one (4-3)squared -2×8=-15.

Which bit is she struggling with?
Write down the equations. Replace each letter with its equivalent number. Do the calculation, not forgetting BODMAS, so eg you calculate 2p (ie 23) and 5r (ie 54) before you do the subtractions and additions

Ask her to pay close attention to negative signs in front of numbers (negative numbers). My son often misses them
out as he steps through the calculations!

Aargh sorry - asterisks betrayed me
"eg you calculate 2p (ie 2x3) and 5r (ie 5x4) before you do the subtractions and additions"

If p = 3, q = 8 and r = 4, evaluate the following:

q - 2p +5r = 8-(2x3) + (5x4) = 8-6+20 =22

(r - p)squared - 2q = (4-3) x (4-3) - (2 x 8)= 1x1 - 16 = -15

22
-15

I think

Thanks all. Am I right in thinking you do additions before subtractions if you're following BODMAS rules? Or does it nit matter?

I would have thought the x first so 2p and 5r
then + next so q - 6+20
8- 26 18??

-18

Doesn't matter, work left to right.
BODMAS is best thought of as
B
O
DM
AS

Although the acronym has addition before subtraction they're on the same level of priority I think, so once you've worked through brackets and powers / roots there's no brackets left, then you work left to right.

Same for multiplication / division, same level of importance so it works left to right.