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SerJibblenuts:
The Probability that Azher, who always walks to work, arrives late on any day is 0.11. Calculate the Probability that, during a period of 20 working days, he is late on exacalty 4 days.

SHOW WORKING

using the binomial theory : p(x)=nCx (p)^x (q)^n-x

let the probability of arriving late be P = 0.11

let the probability of not arriving late be q = 1-0.11= 0.89

n=20, x=4

workings
p(x=4) = 20C4 * (0.11)^4 * (0.89)^16
=4845 * (0.0001464) * (0.1549)
p(x=4)=0.11
conclusion : the probability that he comes late in exactly 4 days is 0.1 i.e 1 in every 10 chances

antladDec 4, 2013

+118725

Josie's checking account balance is 535.23. She deposits a check for 97.83. She then writes a check for 299.98 for a new bicycle and uses her credit card to withdraw $40.00. What is the net change in Josie's account?

Hi Mathicorn and Someone special. (You are special, everyone is)

Special, you have found out how much money is in the account but that was not the question.
The net change is +97.83 - 299.98 - 40 = -242.15

MelodyDec 4, 2013

+118725

Yes, Pi is an irrational number which means that it cannot be written exactly as a fraction or a decimal. It cannot even be writtne exactly as a repeating decimal.
The digits after the decimal point just keep going on forever without even forming a pattern.

MelodyDec 4, 2013

+118725

I have this equation:
2 = sin(x) - cos(x)
How do I find x?

Hi Kytuzian,
-1 < sin(x) < 1
-1 < cos(x) <1

So the only way that this would work would be if sin(x)=1 and Cos(x)=-1
but when sin(x)=1 cos(x)=0 and when cos(x)=-1 sin(x)=0

So there are no solutions.

MelodyDec 4, 2013

+118725

Hi SerJibblenits

The Probability that Azher, who always walks to work, arrives late on any day is 0.11. Calculate the Probability that, during a period of 20 working days, he is late on exacalty 4 days.

I'll not only show you the working I will also do my best to explain.
First you must understand that this answer assumes that the chance of being late on any day is indepentant of any his timeliness on any other day.

Prob of being late = P(a) = 0.11
Prob of not late = P(a with a bar on the top) = 1 - 0.11 = 0.89
The probability of being late for the first 4 days and then not late for the next 16 days would be 0.11^4 * 0.89^16 = 2.2689 * 10^(-5) (to 5 significant figures)

Trouble is, he might be late on the 2nd, 5th 16th and 19th day
or he might be late on the 10th, 11th, 14th and 20th day etc
You need some way to work out how many combinations of 4 days you can choose from 20 days.
And this formula will do it fo you
20C4 = 4845
(There is an nCr button on your calculator)

So the probability that he will be late on exactly four days will be 20C4 * (0.11^4) * (0.89^16) = 0.1099 (correct to 4 dp)

MelodyDec 4, 2013

+118725

Hi Rosey,
The translation did not make a lot of sense.
Did you mean:
A cliff is 40 feet high.
A car drives off the top of the cliff at 10 miles per hour.
How far from the base of the cliff will the car land?

Bing Translation

Hola Rosey,
La traducción no hizo mucho sentido.
¿Quisiste decir:
Un acantilado es de 40 pies de alto.
Un coche conduce a la cima del acantilado a 10 millas por hora.
¿Qué tan lejos de la base del acantilado el coche aterrizará?

MelodyDec 4, 2013

+118725

what's the sqaure root of 0?

This is NOT a ridiculous question.

The answer is 0 because 0*0=0

MelodyDec 4, 2013

+3146

sqrt(x+7) -x+5=0
sqrt(x+7) -x=-5
sqrt(x+7) =-5+x
sqrt(x+7) =-5+x
sqrt(x+7)^2 =(-5+x)^2 (make sure to test both possible solutions at the end)
x+7 =x^2-10x+25
x^2-10x-x+25-7=0
x^2-11x+18=0
x=9 and x=2

test both possible solutions:
[input]x=9; sqrt(x+7) -x+5[/input]
[input]x=2; sqrt(x+7) -x+5[/input]
so only x=9 is a solution.

adminDec 4, 2013

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