for A i got 3 and for B i got 2.5
I know that their gradients will multiply together to give -1 but from the gradient I got they don't equal -1 so does that mean theyre not perpendicular or did i do my calculations wrong?

Your calculations are wrong. From the answers you have given though, I suspect for A you have made a division error and B you have subtracted something incorrectly. If you would like to PM me a photo of your working out I can tell you where you've gone wrong :smile:

Reply 26

username5118974

Original post by mqb2766

Get the gradient of each line first. How do you calculate them - see the maths is fun link.

I have done this, I got A=3 B=2.5. I followed the steps on the website are my answers incorrect?

Reply 27

mqb2766

Original post by Kakakaty

The change in Y divided by change in X

Original post by Kakakaty

I have done this, I got A=3 B=2.5. I followed the steps on the website are my answers incorrect?

Yes for the third time. What is the change in y and the change in x?

Reply 28

Always_Confused

Original post by Kakakaty

I have done this, I got A=3 B=2.5. I followed the steps on the website are my answers

Line A: two points on the line are 1: (3, 5) and 2: (6,6). x2 - x1 = 6 - 3 = 3. y2 - y1 = 6 - 5 = 1.
Gradient = (y2 - y1)/(x2 - x1) = 1/3
Do the same thing for two points on line B.

Do the gradients multiply to -1?
If yes: lines are perpendicular
If no: lines are not perpendicular

Reply 29

username5118974

This is an image of what I did so for line A I have the y value (2) and the x value (6) 2/6 = 0.3. and then for line B I have the y value of 5 and the x value of 2. 5/2 = 2.5. Where am I going wrong?

Reply 30

mqb2766

Original post by Kakakaty

This is an image of what I did so for line A I have the y value (2) and the x value (6) 2/6 = 0.3. and then for line B I have the y value of 5 and the x value of 2. 5/2 = 2.5. Where am I going wrong?

Line A is now correct 0.333... Line B goes down, so what does that mean for the gradient (change in y)?

Reply 31

username5118974

Original post by mqb2766

Line A is now correct 0.333... Line B goes down, so what does that mean for the gradient (change in y)?

-2.5 ?

Reply 32

mqb2766

Original post by Kakakaty

-2.5 ?

Yes
So their product is ?

Reply 33

username5118974

Original post by mqb2766

Yes
So their product is ?

-0.75 ?

Reply 34

mqb2766

Original post by Kakakaty

-0.75 ?

Well it's -5/6 without the rounding.
It's close to -1 but not quite equal.
The lines are almost perpendicular (eyeballing them) but not quite when you do the numbers.

Reply 35

username5118974

Original post by mqb2766

Well it's -5/6 without the rounding.
It's close to -1 but not quite equal.
The lines are almost perpendicular (eyeballing them) but not quite when you do the numbers.

Woooo thankyou for you help.
One last thing
Would this be ok for my final answer -

The lines A and B would not be perpendicular this is because in order for them to be perpendicular their gradients must multiply together to get -1. Line A's gradient is 0.333.... and Line B's gradient is -2.5. When multiplying these together you get -5/6 (0.83333...). Therefore, this means they are not perpendicular as they do not multiply together to get -1.

Reply 36

mqb2766

Original post by Kakakaty

Fine, but I'd really recommend you do some more practice on the line / gradient basics.

Reply 37

username5118974

Original post by mqb2766

Fine, but I'd really recommend you do some more practice on the line / gradient basics.

I agree, I really need to, It seems the information never stays in my brain. I've tried finding resources online of where I can practice linear graphs, gradients etc but I can't find many resources which have ways to practice.

Reply 38

mqb2766

Original post by Kakakaty

drfrostmaths.com
you can get questions about all parts of the syllabus graded 1-4, including this topic.
Tbh, most gcse maths sites will have questions about this. Just have a look at the usual suspects, after trying drfrostmaths.