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 #12
avatar+118723 
+3

Thanks Ginger, I'm going to try answering independently of you and  see if we get the same answer :))

 

To answer Melody's question, you pick three numbers from 1 to 20. Once you pick a number from there, it can not be chosen again. You also pick a number from 21 to 30. You pick these numbers at random. ( I never played lottery before, so I'm doing my best.) Again, three numbers from 1 to 20 and one number from 21 to 30 is chosen. These numbers are the winning numbers. If it happens that you match at least two of the numbers from 1 to 20 with the winning numbers, or you match the Superball number, you win a prize. ( The order doesn't matter)

 

ok, I am going to pretend that the winning numbers are chosen first.  So there are 3 low winning numbers but you only need two of them OR one high winning number and that is the one you need. This will make no difference to the outcome.

Plus there are 2 independent events happening here.

 

The chance of you getting the high winning number is 1 in 10 that is the easy bit

 

The number of ways that 3 numbers can be chosen from 20 is 20C3 = 1140   just like Ginger said.

The number of ways that I can get all three numbers is 1

I can get 3 pairs of 2 numbers , just as Ginger said.

The number of ways i can get any one of these pairs and not the third winning number is  17

17*3= 51

So I think there are 51 ways of chosing 2 winning small numbers and not not getting the third.

So that makes a total of 52 ways of getting a winning set of smal numbers.

 

So I think that the chance of getting 2 or 3 small numbers + getting the big one is

\(\frac{52}{1140}\times\frac{1}{10}=\frac{52}{11400}\)

 

Which means that the chance of winning is  

\(\frac{52}{1140}+\frac{1}{10}-\frac{52}{11400}\\ =\frac{520}{11400}+\frac{1140}{11400}-\frac{52}{11400}\\ =\frac{520+1140-52}{11400}\\ =\frac{1608}{11400}\\ =\frac{67}{475}\\ \approx 0.141 \)

 

Ginger's answer and mine are only slightly different. I think it is just rounding error.

If so mine is closer because i didn't round anything until the very end.  cheeky

Jul 2, 2017
 #11
avatar+2236 
0
Jul 2, 2017
 #10
avatar+118723 
0
Jul 2, 2017
 #1
avatar+2446 
+2

\((x-\sqrt{48})^2\leq\frac{49}{3}\) 

 

I am sorry if I have interpreted your inequality incorrectly. I am fairly certain that the equation above is what you were attempting to convey.

 

\((x-\sqrt{48})^2\leq\frac{49}{3}\) Undo the square by square rooting both sides of the inequality.
\(x-\sqrt{48}\leq|\sqrt{\frac{49}{3}}|\) Remember the square root rule that states that \(\sqrt{\frac{a}{b}}=\frac{\sqrt{a}}{\sqrt{b}}\). I like to think of it as "distributing" the square root into both the numerator and denominator. Also, the square root function always results in a negative and positive answer. That's why the absolute value sign is there.
\(x-\sqrt{48}\leq|\frac{\sqrt{49}}{\sqrt{3}}|\) Simplify the fraction on the right side of the equation.
\(x-\sqrt{48}\leq|\frac{7}{\sqrt{3}}|\) Let's rationalize the right hand side of the equation by multiplying the numerator and denominator by 
\(\frac{7}{\sqrt{3}}*\frac{\sqrt{3}}{\sqrt{3}}=\frac{7\sqrt{3}}{3}\) Reinsert this back into the inequality.
\(x-\sqrt{48}\leq|\frac{7\sqrt{3}}{3}|\) The absolute value results in 2 answers: the positive and negative. Let's split that up.
\(x-\sqrt{48}\leq\pm\frac{7\sqrt{3}}{3}\)  

 

Now, we must evaluate each inequality separately. The one for the plus and the one for the minus. To make it easier, I'll solve both one at a time! I'll do the positive version first:

 

\(x-\sqrt{48}\leq\frac{7\sqrt{3}}{3}\) Add \(\sqrt{48}\) to both sides.
\(x\leq\frac{7\sqrt{3}}{3}+\sqrt{48}\) First, I'll make\(\sqrt{48}\) into simplest radical form.
\(\sqrt{48}=\sqrt{16*3}=\sqrt{16}\sqrt{3}=4\sqrt{3}\) Ok, because this radical is in simplest radical form, reinsert it back into the equation. 
\(x\leq\frac{7\sqrt{3}}{3}+\frac{4\sqrt{3}}{1}\) Put \(\frac{4\sqrt{3}}{1}\) into a common denominator so that it is possible to add them together.
\(\frac{4\sqrt{3}}{1}*\frac{3}{3}=\frac{12\sqrt{3}}{3}\) Now that this fraction has a common denominator, let's add them together.
\(x\leq\frac{7\sqrt{3}}{3}+\frac{12\sqrt{3}}{3}\) Add the fractions together. 
\(x\leq\frac{19\sqrt{3}}{3}\) Time to solve the second part of the equation.
   

 

Now, we have to solve for the other scenario, \(x-\sqrt{48}\geq-\frac{7\sqrt{3}}{3}\). Now, this is a tad difficult to explain, but the absolute value function does funny things to an inequality. The rule is that \(|f(x)|\leq a\Rightarrow f(x)\leq a\hspace{1mm}\text{and}\hspace{1mm}f(x)\geq -a\)

 

\(x-\sqrt{48}\geq-\frac{7\sqrt{3}}{3}\) Solve and isolate x by adding \(\sqrt{48}\) to both sides.
\(x\geq-\frac{7\sqrt{3}}{3}+\sqrt{48}\) Put \(\sqrt{48}\) into simplest radical form and put in common denomator. Because I have already done this in the previous equation, I'll just skip.
\(x\geq-\frac{7\sqrt{3}}{3}+\frac{12\sqrt{3}}{3}\) Add the fractions together now.
\(x\geq\frac{5\sqrt{3}}{3}\)  
   

 

Now, put the solutions together.

 

\(\frac{5\sqrt{3}}{3}\leq x\leq \frac{19\sqrt{3}}{3}\)

.
 #8
avatar+2236 
+1

Yep seems like a normal lottery to me, Except that the super balls would normally be numbered from 1 to 10 instead of 21 to 30.

 

 

In lotteries with super balls, the super balls are a separate set and a different color, and the ball is drawn separately from the other balls – in other words, these are independent events.  If they were not independent then a super ball may not be drawn at all or three super balls may be drawn and none of the others.

 

To find the over all probability

 

First, calculate the probability of matching 2 of three numbers drawn from a pool of 20 numbered balls.

 

1)       Number of ways to select 3 balls from 20 

                20! / (17! * 3!)  =  nCr(20,3) = 1140

 

2)       Number of ways select to 2 balls from 3 balls

                (3!) / ((2!)*(3-2)!) = 3

 

3)       Number of ways to select 2 matching balls and one none matching ball in a draw of 3                      from 20 balls

                (20-3)! / (((20-3) - (3-2))! * (3-2)!) = 17

 

4)       Number of ways of matching 2 balls in a draw of 3 from 20 balls

                 3*17= 51

 

5)       Probability of matching 2 balls in a draw of 3 from 20 balls

           51/1140 = 0.04473684 or 1 in 22.353

                 

Second, calculate the probability of matching 1 of 10 numbers drawn

This is easy it is just 1 in 10.

 

Winning requires a match on the first OR second draw. (You could match both, but that is irrelevant here.)

 

The probability of winning is the same as the rate of winning.  On average, a win will occur 1 in every 22.353 draws for the first set, or 1 in every 10 draws for the second set.

 

To find the over all probability of having a win, average the two rates.

 

The word “rate” offers a clue for the proper type of average to use. When averaging rates, use the harmonic average.

 

H = 2/ (1/10 + 1/22.353) = 13.8182

 

This equates to each of the draw events having a (1/13.813) probability of matching; but remember there are 2 events, so multiply this by 2.  (1/13.813) * 2 =  0.1447

 

Over all probability 14.47%

Jul 2, 2017
 #1
avatar+2446 
+2

Evaluating these algebraid expressions just requires you to substitute in the values given for the variable. Let's do the first one together:
 

1. \(N^2-25\)

 

a) When n=-10

 

\(N^2-25\) Replace N, the variable, with -10 and evaluate from there.
\((-10)^2-25\) Do \((-10)^2=-10*-10=100\) first so to adhere to the order of operations. 
\(100-25\)  
\(75\)  
   

 

The process repeats for the other values for N

 

b) n=-5

 

\(N^2-25\)  
\((-5)^2-25\)  
\(25-25\)  
\(0\)  
   

 

c) n=1/2

 

\(N^2-25\)  
\((\frac{1}{2})^2-25\) Remember that squaring a fraction follows the rule that \((\frac{a}{b})^2=\frac{a^2}{b^2}\)
\(\frac{1^2}{2^2}-25\) Simplify the fraction.
\(\frac{1}{4}-25\) Change 25 to an improper fraction so that you can subtract it from 1/4.
\(\frac{25}{1}*\frac{4}{4}=\frac{100}{4}\) Now that we have changed 25 to a fraction with a common denominator, reinsert it back into the equation.
\(\frac{1}{4}-\frac{100}{4}\) Subtract the fractions.
\(-\frac{99}{4}=-24\frac{3}{4}\) The fraction is already in simplest form. I've provided both versions of the answer.
   

 

d) n=9

 

\(N^2-25\)  
\(9^2-25\)  
\(81-25\)  
\(56\)  
   

 

I'll do half of the next one and the rest are up to you to complete:

 

2. \(\frac{-7d+14}{2}\)

 

a) d=2

 

\(\frac{-7d+14}{2}\) Substitute the given value for d, 2.
\(\frac{-7*2+14}{2}\) Do -7*2 first.
\(\frac{-14+14}{2}\) Simplify the numerator by calculating -14+14.
\(\frac{0}{2}=0\)  
   
   

 

b) d=-2

 

\(\frac{-7d+14}{2}\)  
\(\frac{-7*-2+14}{2}\) A negative times a negative always results in a positive.
\(\frac{14+14}{2}\)  
\(\frac{28}{2}\) Divide 28 by 2.
\(14\)  
   
Jul 1, 2017

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