Hey, got my maths exam in the morning and I've been posting some of the problems here on Face Punch.
Doing some last minute study and I'm shitting butterfly's out my arse, and I need help with these last 2 questions, they are the only ones on my paper I don't understand.
1st Question
[quote]
It costs you 10 euros per backpack to manufacture and distribute backpacks. If the backpacks sell at x euros each (where 15 <= x <= 100), the number sold is
given by
a
_______ + b (100 - x) = n
x - 10
where a and b are positive constants. What selling price will bring a maxinlum
profit?[/quote]
2nd Question
[quote] A survey is carried out on a computer network. The probability that a log onto the network is successful is 0.97. Find the probability that exactly six out
of eight users that attempt to log on will do so successfully[/quote]
I hope that makes sense, the formatting is a bit off because I copied and pasted, but it is A over X - 10 in the first part, then + b etc.
Cheers for any helps men.
WELL I'D HELP YOU WITH YOUR MATHS SON BUT MY MATHS BRAIN IS ALL OUT OF ITS MATHS JUICE.
Funny. Anybody here got any solutions?
[QUOTE=Over-Run;31750673]Hey, got my maths exam in the morning and I've been posting some of the problems here on Face Punch.
Doing some last minute study and I'm shitting butterfly's out my arse, and I need help with these last 2 questions, they are the only ones on my paper I don't understand.
1st Question
2nd Question
I hope that makes sense, the formatting is a bit off because I copied and pasted, but it is A over X - 10 in the first part, then + b etc.
Cheers for any helps men.[/QUOTE]
For the first, I get stuck at:
x(a-b) - 10(a+10b) = n so if you get to know a and b it would be a lot easier.
The second one is reaally weird. The probality that 6 out of 8 people log in successfully is 6/8*0.97 = 0.7275
Could be wrong though.
The second one is about 0.075%.
[editline]15th August 2011[/editline]
First is $55.
[QUOTE=JohnnyMo1;31754219]The second one is about 0.075%.
[editline]15th August 2011[/editline]
First is $55.[/QUOTE]
How do you get 55?
Profit per item is the sale price minus the cost, (x-10). Total profit is that times the number sold, n(x-10). Multiply that equation through by (x-10) and you get a + b(100-x)(x-10) = n(x-10). Let's label n(x-10) as p for profit. So p = a + b(-x[sup]2[/sup] + 110x - 1000). Differentiate that and set the result to zero. 0 = b(-2x + 110). 0 = -2x + 110. -2x = -110. x = 55.
[QUOTE=JohnnyMo1;31757856]Profit per item is the sale price minus the cost, (x-10). Total profit is that times the number sold, n(x-10). Multiply that equation through by (x-10) and you get a + b(100-x)(x-10) = n(x-10). Let's label n(x-10) as p for profit. So p = a + b(-x[sup]2[/sup] + 110x - 1000). Differentiate that and set the result to zero. 0 = b(-2x + 110). 0 = -2x + 110. -2x = -110. x = 55.[/QUOTE]
Man how are you a beast at maths haha thanks a lot for all the help, and cheers other dude for trying with the 2nd question, even if it isn't right it still makes more sense than what I could do.
Also, did you do commander204's method for the second question to get that answer or?
No. To find the probability of a bunch of events with probabilities like that you multiply them together.
You want six successes and two failures. The chance of a failure is 1 - the chance of a success. (0.97) * (0.97) * (0.97) * (0.97) * (0.97) * (0.97) * (1-0.97) * (1-0.97) = (0.97)[sup]6[/sup] * (0.03)[sup]2[/sup]. Punch that motherfucker into a calculator.
[editline]16th August 2011[/editline]
Gives me 0.0007496748044361 or about 0.075%.
Awh man thank you so much ha I might just pass this exam now! Cheers buddy!
You're welcome
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