OL Maths Help

J_E

Hey guys, I dropped down to OL Maths about 2-3 weeks ago, I've been getting along fine but I've stumbled upon this question and it's really left me a bit confused. It's 2006, Q6 (b).

"The temperature, C in degrees Celsius, of a liquid in an insulated container is related to time t, in hours, by C=86-6t"

Draw the straight line graph of this relation, putting t on the horizonal axis, for 0<=t<=8.

I've done a few acceleration questions but this one has me pretty stumped, anyone have any idea to do this? The answer has a negative gradient.

pajero12

The question goes from 0 > 8

So put in the number into the equation in place of t

I.E Using 0= 86-6(0) So the x co-ordinate = 0 y= 86

Using 1 : 86-6(1) = 80 x=1 y=80

That make sense?

Gavarn

I'm sure you know this, but go to your calculator - "Mode" - "Table" - "f(X) =" Fill in 86-6X *press =*- Start 0 *press =* - End 8 *press =* - Step 1 *press =*- There is a table that is on the screen, x is your x value and f(x) is your y value. Plot on graph temp as y axis, hours as x axis, notice going down from (0,86) down. Basically the liquid is losing temperature. Then part (ii) you go up from 5.5 and across and put answer from your graph. For part (iii) go across from both 80 degrees and 60 degrees and down. The difference in time from both = answer. Hope this helps, it's pretty simple, I found it hard when I dropped down too! Looking for something more to it!

alltakennamess

I actually made my teacher do that in class before we finished!
It looks complicated but its actually easy

When it says C=86-6t and you need to get 0<t<8 you just sub in 0,1,2,3 etc into the equation. Like for 0 it would be 86-6(0) which is equal to 86 meaning the point is (0,86) and then for 1 you sub it in like 86-6(1) and get 80 so point is (1,80) and so on to 8

Then for the graph the horizontal axis will be time as it says in question so go from 0-8 and then the verticle axis will be the temp. If you work it all out it starts at 38 and goes up to 86 and then you just plot your points like on any other graph!

Ok i hope this helped and that it wasnt too confusing cause its kinda hard to explain on this

J_E

Gavarn wrote: »

I'm sure you know this, but go to your calculator - "Mode" - "Table" - "f(X) =" Fill in 86-6X *press =*- Start 0 *press =* - End 8 *press =* - Step 1 *press =*- There is a table that is on the screen, x is your x value and f(x) is your y value. Plot on graph temp as y axis, hours as x axis, notice going down from (0,86) down. Basically the liquid is losing temperature. Then part (ii) you go up from 5.5 and across and put answer from your graph. For part (iii) go across from both 80 degrees and 60 degrees and down. The difference in time from both = answer. Hope this helps, it's pretty simple, I found it hard when I dropped down too! Looking for something more to it!

Oh man, this is brilliant, I didn't even realise my calculator could do this. This is one of the first times I've had to graph stuff properly because I never did it in HL. Thanks a million guys. I'll let you know how this goes. Just wondering, how do I put in the x?

Edit: Ah, figured it out.

Gavarn

No problem Makes me feel like I have revised something today! :P If you have anything else you get confused about before Friday, send me a PM! Good Luck!