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Maths year 11

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Original post by z_o_e
Do I not multiply them?

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Yes, you do multiply them, but you had multiplied them incorrectly

2×−25=−45 2 \times -2\sqrt5 = -4\sqrt5

You had written 2−25 2 - 2\sqrt5 instead.
Reply 1481
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Original post by K-Man_PhysCheM
Yes, you do multiply them, but you had multiplied them incorrectly

2×−25=−45 2 \times -2\sqrt5 = -4\sqrt5

You had written 2−25 2 - 2\sqrt5 instead.




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Original post by z_o_e
What do you mean like terms? Do I add all the surds up from each bracket?

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You multiply the brackets out, as I had done, and then you collect the terms which can be collected.

18−45+95−10 18-4\sqrt5+9\sqrt5-10 is what you get from multiplying out the brackets (you had already done this, bar one term which was incorrectly multiplied).

You can collect the single numbers together (18−1018 - 10) and collect the terms with the same surds together 995−459\sqrt5 - 4\sqrt5, and then simplify.
Reply 1483
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Original post by K-Man_PhysCheM
Yes, you do multiply them, but you had multiplied them incorrectly

2×−25=−45 2 \times -2\sqrt5 = -4\sqrt5

You had written 2−25 2 - 2\sqrt5 instead.


You told me I multiplied them all wrong?

So is above right?
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Original post by z_o_e
You told me I multiplied them all wrong!

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You had only multiplied that one incorrectly. The rest were correct.

I had said:

" The is not correct, because , not



Now you need to collect like terms. "
Reply 1485
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Original post by K-Man_PhysCheM
You had only multiplied that one incorrectly. The rest were correct.

I had said:

" The is not correct, because , not



Now you need to collect like terms. "


Ergh

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Past papers !
Reply 1487
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Original post by K-Man_PhysCheM
You had only multiplied that one incorrectly. The rest were correct.

I had said:

" The is not correct, because , not



Now you need to collect like terms. "




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Original post by z_o_e


Correct. Now remember that @RDKGames' question was about a triangle, so how do you find the area of a triangle?

Spoiler

Then you need to find 4.1% of that area to answer the question.
Reply 1489
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Original post by K-Man_PhysCheM
Correct. Now remember that @RDKGames' question was about a triangle, so how do you find the area of a triangle?

Spoiler

Then you need to find 4.1% of that area to answer the question.


Divide it by 2

And then divide it by 4.1 and times it by 100?

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Original post by z_o_e
Divide it by 2

And then divide it by 4.1 and times it by 100?

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Divide by 2 is correct, but are you sure that you would calculate 4.1% by dividing by 4.1 and multiplying by 100? Wouldn't that give a much larger number?

E.g 8.24.1×100=200 \dfrac {8.2}{4.1} \times 100 = 200 .

200 couldn't be 4.1% of 8.2... 200 is much larger than 8.2 !!

But if you try the other way:

8.2100×4.1=0.3362\dfrac {8.2}{100} \times 4.1 = 0.3362 , which looks about right.

Hence, to get a percentage of something, first DIVIDE by 100, then multiply by the percentage you need to find.

However, in that question, do NOT use a calculator: you need to leave it in the form:
AB(c3+55) \frac{A}{B}(c^3 + 5\sqrt5)

Note: you already have the c3+55c^3 + 5\sqrt5 bit:
8+55=23+558+5\sqrt5 = 2^3+5\sqrt5.

Hence all you need to do is to find the AB\frac{A}{B} bit.
(edited 7 years ago)
Original post by K-Man_PhysCheM

Hence, to get a percentage of something, first DIVIDE by 100, then multiply by the percentage you need to find.


Or just turn 4.1% into 4.1100=411000\frac{4.1}{100}=\frac{41}{1000} straight away which makes the working out smoother.
(edited 7 years ago)
Original post by RDKGames
Or just turn 4.1% into 4.1100=411000\frac{4.1}{100}=\frac{41}{1000} straight away which makes the working out smoother.


x100×y≡y100(x)\frac{x}{100}\times{y} \equiv \frac{y}{100} (x) in my head, and I would just immediately convert between the two, but yeah, I agree the latter would be much neater and easier for the answer format.
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Original post by K-Man_PhysCheM
x100×y≡y100(x)\frac{x}{100}\times{y} \equiv \frac{y}{100} (x) in my head, and I would just immediately convert between the two, but yeah, I agree the latter would be much neater and easier for the answer format.




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Reply 1494
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Original post by z_o_e


Don't use a calculator! Remember, you have to leave the answer in the form:

AB(c3+55)\frac{A}{B}(c^3+5\sqrt5)

Moreover, that is NOT how you work out percentage. Multiply by 4.1 and divide by 100, or in other words:

ans×4.1100≡411000×c3+552ans\times\dfrac{4.1}{100} \equiv \dfrac{41}{1000}\times\dfrac{c^3+5\sqrt5}{2}
Reply 1496
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Original post by RDKGames
Nope. Don't tell you forgot how to expand brackets with surds...


How are these?


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Original post by z_o_e


All correct. On the last one there shouldnt be a 2 next to 9\sqrt9 though
Reply 1498
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Original post by RDKGames
All correct. On the last one there shouldnt be a 2 next to 9\sqrt9 though


Oh alright x



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Reply 1499
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Original post by RDKGames
All correct. On the last one there shouldnt be a 2 next to 9\sqrt9 though


How would I do this one?


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