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C2 question

https://gyazo.com/9c618f6e7830c2a87fd865258b272ea3

Can someone give some assistance with part B please?? Thanks :smile:
@iMacJack
Each unit on the axis is worth 8cm. You are multiplying both axis by each other in order to find the area R. Therefore if you multiply the area R by 64 (8 squared) then you will get the area in cm. Then its just a simple case of multiplying the area by the depth to get the volume
Reply 2
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iMacJack
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Original post by Snasher350
@iMacJack
Each unit on the axis is worth 8cm. You are multiplying both axis by each other in order to find the area R. Therefore if you multiply the area R by 64 (8 squared) then you will get the area in cm. Then its just a simple case of multiplying the area by the depth to get the volume


Why 64? I don't understand why you times it by 8^2?
Original post by iMacJack
Why 64? I don't understand why you times it by 8^2?


It says that 1 unit is 8cm
And cross section=length*width
So you need to do 8*8=64(both axis)
Then you multiply it by whatever you got in part a and then by the height/thickness of 2
Reply 4
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iMacJack
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Original post by 4nonymous
It says that 1 unit is 8cm
And cross section=length*width
So you need to do 8*8=64(both axis)
Then you multiply it by whatever you got in part a and then by the height/thickness of 2


But on the X axis surely there's two units?
Original post by iMacJack
Why 64? I don't understand why you times it by 8^2?


Say if you had a rectangle which was 5 units high and 7 units wide. Then obviously A (area) would equal 35. A = 5 units x 7 units = 35 units squared

But now if we want the area in cm and we are told that 1 unit = 8 cm
We could do this : 5 x 8 = 40 cm high and 7 x 8 = 56 cm wide

Therefore are new area would equal 2240 cm squared.

In the case of the integration it is much easier to just multiply the answer for R by 8 squared. And we can do this since (using the example above)
(5x8) x (7x8) = 5 x 7 x 64
Original post by iMacJack
But on the X axis surely there's two units?


Yes but you're already taking that into account by using the answer from part a which uses the 2 in the trapezium rule. You are then multiplying this by 8 because each unit is 8cm. And then by 8 again for the other axis
Reply 7
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iMacJack
OP
16
Original post by Snasher350
Say if you had a rectangle which was 5 units high and 7 units wide. Then obviously A (area) would equal 35. A = 5 units x 7 units = 35 units squared

But now if we want the area in cm and we are told that 1 unit = 8 cm
We could do this : 5 x 8 = 40 cm high and 7 x 8 = 56 cm wide

Therefore are new area would equal 2240 cm squared.

In the case of the integration it is much easier to just multiply the answer for R by 8 squared. And we can do this since (using the example above)
(5x8) x (7x8) = 5 x 7 x 64


But on the x axis there is two units?
Reply 8
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iMacJack
OP
16
Original post by 4nonymous
Yes but you're already taking that into account by using the answer from part a which uses the 2 in the trapezium rule. You are then multiplying this by 8 because each unit is 8cm. And then by 8 again for the other axis


Ohhhhhhhhh.. okay... I see!! Thank you
Original post by iMacJack
Ohhhhhhhhh.. okay... I see!! Thank you


No problem that was a nice question for me to have a try at too so thanks. And good luck with the exam
Reply 10
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iMacJack
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Original post by 4nonymous
No problem that was a nice question for me to have a try at too so thanks. And good luck with the exam


You too - best of luck

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