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Maths year 11

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Reply 1142
Original post by K-Man_PhysCheM
Yep, correct.


Greatest difference one too?

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Ooh, are you sure about the greatest difference? Try subtracting the LB of the short pencil from the UB of the longer pencil, and see if you get a bigger difference.


Correct. (Referring to the last post on prev page)

Original post by K-Man_PhysCheM
Haha, yeah, that must be annoying. Having read some of your posts, you are very good at explaining. I think I'll let you do the explaining (I think my explanations were too convoluted and confusing) but I'm going to keep posting questions for @z_o_e if she asks for any more.


Aha thanks. Sure go ahead, I find it difficult to think of questions on the spot sometimes. :tongue:
Original post by z_o_e
Greatest difference one too?

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You get the biggest difference by subtracting something very small FROM something very big.
Reply 1146
Original post by RDKGames
You get the biggest difference by subtracting something very small FROM something very big.


I got 5CM

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That's correct.
Reply 1148
Original post by RDKGames
That's correct.




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Get your UB and LB for 5cm. Then use them accordingly to get the largest area and then smallest circumference.


OK, some more questions if you want:

5) One train carriage is 20m long while another is 15m long, both to the nearest metre. What is the smallest possible difference in length?

6) A cube has side length 40cm, to the nearest cm. What is the maximum possible volume of the cube?

7) Each fish in an aquarium needs at least 5 m^3 of space to be legal by the government of Fishville. An aquarium fish tank is shaped as a cuboid, and has side lengths 20m, 30m and 10m, to the nearest metre.
a) What is the minimum possible volume of the fish tank?
b) How many fish could be legally placed in the tank, if it is the minimum volume?
(edited 7 years ago)
Original post by K-Man_PhysCheM
...government of Fishville...


Oh I miss the stupid contexts of GCSE questions lol... I hope Bob is still delivering some mail and spends less on fuel than his competitor Greg.
Original post by RDKGames
Oh I miss the stupid contexts of GCSE questions lol... I hope Bob is still delivering some mail and spends less on fuel than his competitor Greg.


Wait, you mean A-level Maths doesn't include silly context????
Original post by K-Man_PhysCheM
Wait, you mean A-level Maths doesn't include silly context????


Of course not. That would be pointless. Only in sometimes in Statistics and Decision modules would you be given context but at least that context has information that you can use in your working. None of this "The driver's name is Bob" crap.
Reply 1154
Original post by K-Man_PhysCheM
OK, some more questions if you want:

5) One train carriage is 20m long while another is 15m long, both to the nearest metre. What is the smallest possible difference in length?

6) A cube has side length 40cm, to the nearest cm. What is the maximum possible volume of the cube?

7) Each fish in an aquarium needs at least 5 m^3 of space to be legal by the government of Fishville. An aquarium fish tank is shaped as a cuboid, and has side lengths 20m, 30m and 10m, to the nearest metre.
a) What is the minimum possible volume of the fish tank?
b) How many fish could be legally placed in the tank, if it is the minimum volume?




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Reply 1155
Original post by K-Man_PhysCheM
OK, some more questions if you want:

5) One train carriage is 20m long while another is 15m long, both to the nearest metre. What is the smallest possible difference in length?

6) A cube has side length 40cm, to the nearest cm. What is the maximum possible volume of the cube?

7) Each fish in an aquarium needs at least 5 m^3 of space to be legal by the government of Fishville. An aquarium fish tank is shaped as a cuboid, and has side lengths 20m, 30m and 10m, to the nearest metre.
a) What is the minimum possible volume of the fish tank?
b) How many fish could be legally placed in the tank, if it is the minimum volume?


For 6 do I find the UB?

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Ah, be careful, the question asks for the smallest possible difference this time. To make a small number, you take a not too big number from a fairly big smaller number.
Original post by z_o_e
For 6 do I find the UB?

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Yes, and then use that value to find the volume of the cube.
Reply 1158
Original post by K-Man_PhysCheM
Yes, and then use that value to find the volume of the cube.


What do you mean find the volume of the cube?
Should I divide the UB by 3?

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Original post by z_o_e
What do you mean find the volume of the cube?
Should I divide the UB by 3?

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For the first question, what if you use the upper bound of the shorter train (and the lower bound of the longer train)? Do you get an even smaller difference?

The volume is the space that an object occupies. It's a bit like area, but for 3D objects, like cubes.

To work out the area of a rectangle, you would multiply the lengths of its two perpendicular sides together. In a square, both side lengths are the same, so to find it's area you square the side length (multiply it by itself).

area.JPG

Volume brings this into 3-Dimensions: to calculate the volume of a cuboid, you need to multiply together the three side lengths; Volume (of cuboid) = a x b x c.

In a cube, all sides are the same length, so you need to do Volume (of cube) = a x a x a = a^3 (side length cubed). The maximum volume will come from cubing the upper bound of the side lengths. These formulas will* be given to you at the front of the paper or on a separate formula sheet, so you don't need to memorise them: you can just check the sheet.

EDIT: *Those formulas might be given to you, it will depend on your exam board though.
(edited 7 years ago)

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