A) 11.5 - 1.8 = 9.7
B) VC=1000 X 9.7 / 60 X (10 X 0.5) = 32.3
32.3 X 0.866 = 27.7 ?
How is this wrong GOD ???
I don't know what the answer is but I get 0.467.
You haven't expanded the brackets in part b.
So 60(10x0.5) = 600x30 which equals 18000.
9700/18000= 0.54
0.54 x 0.866 = 0.467
Could be wrong
You haven't expanded the brackets in part b.
So 60(10x0.5) = 600x30 which equals 18000.
9700/18000= 0.54
0.54 x 0.866 = 0.467
Could be wrong
Hi Andrew,
I haven’t looked at the question but you don’t “expand” the brackets. 60(10x0.5) is the same as 60x10x0.5. The only time you would expand the brackets is if you had a variable or unknown within the brackets.
I haven’t looked at the question but you don’t “expand” the brackets. 60(10x0.5) is the same as 60x10x0.5. The only time you would expand the brackets is if you had a variable or unknown within the brackets.
Hi Ashley, I don't believe 60(10x0.5) is the same thing as 60x10x0.5 otherwise the brackets wouldn't need to be there? Take a look at the first example on this page - https://www.mathsisfun.com/algebra/expanding.html
Hi Andrew,
I believe the brackets may have been used to highlight that the circuit protection value was being halved (or x 0.5) as part of the exception clauses and to keep this "grouped" together. From a purely mathematical standpoint, having the brackets in place in this situation provides no benefit or reason. The brackets purely mean to solve what's within the brackets before doing anything else within the entire formula.
I believe the brackets may have been used to highlight that the circuit protection value was being halved (or x 0.5) as part of the exception clauses and to keep this "grouped" together. From a purely mathematical standpoint, having the brackets in place in this situation provides no benefit or reason. The brackets purely mean to solve what's within the brackets before doing anything else within the entire formula.
e.g.
60(10 x 0.5) = 60 x 5
= 300
Now, ignoring the brackets and solving from left to right:
60 x 10 x 0.5 = 600 x 0.5
= 300
This only works if you only have multiplication or division within your equation. If there is any addition or subtraction, you need to follow BODMAS (or other variants of this).
The example on the link is where you have an addition within the brackets, and yes, expanding the brackets using your method would work, but is pointless if you have defined values within the brackets. For defined values, simple solve the equation within the brackets and then multiple the answer by the number outside of the brackets.
i.e. with an addition sign (+) in the brackets, you would then add these values together before multiplying this value with the number outside of the brackets.
Using the example in the link you provided, this would be the method of answering the question:
3 x (5 + 2) = 3 x 7
= 21
This is the same as:
3x5 + 3x2
= 15 + 6
= 21
Method 1 is much quicker and easier and you would only really expand the brackets if you had an unknown value that you would need to solve the equation for (or transpose):
e.g.
Solve for a:
10(2a + 4) = 100 => now we will expand the equation
20a +40 = 100 => now to transpose to make "a" the subject
20a = 100-40
20a= 60
a = 60/20
a = 3
It's important to understand algebra and when it applies. If you have a basic formula and all the values are known/provided, you do not need to use algebra, you would just need to know the order of operation i.e. what calculations to do and in what order.
Correct
Well explained, thanks.
Hi Jett,
I think this might just be a case of a rounding issue with the question/answer.
If you keep the entire value of Vc (i.e. 32.333333333) in your calculator and not round it to 32.3V before multiplying by 0.866, it works. You then get 28.0V.
Nice Work Ashley. It is a rounding issue. I like people to keep things to at least 3 significant figures but I/m getting soft in my old age and I have now ajusted the tolerance to make 27.7 Correct.
I know this is kind of resolved but I'm confused 32.3 x 0.866 = 27.9718 round that you should get 28?
You have raised a very good point. rounding would normally dictate that we round up. Given that the number we have calculated is a maximum 28 would techniclly be incorrect. But we are splitting hairs here and any assessor who marks you wrong for it is being a tosser. I think I will ajust the tollerance in the question.
Thanks for pointing this out.
Thanks for pointing this out.