CPhill

Correct, RP....!!!!

6.  Less than 2  = 1/10

    Greater than 7  = 3/10

So  1/10 + 3/10  =  4/10   =  2/5

7.   Area A  = pi (4)^2  =  16pi

      Area B  =  Area B  - Area A  =  pi (4 + 4)^2 - pi (4)^2    =     48 pi     

       Area C  =  pi (4 + 4 + 4)^2  - pi (4 + 4)^2   =    144pi  - 64pi   = 80pi   (3)

      Area D  =  pi (4 + 4 + 4 + 4)^2 - Pi(4 + 4 + 4)^2  =  256pi  - 144pi  =  112pi

Prob B  =     Area B  / sum of the areas  =  48pi  /  ( [ 16 + 48 + 80 + 112] pi  )  =

                      48  / 256  =

                       3 / 16

Pars all three holes  =  (.78)^3  = .475  

Pars on any  2  of the holes  = C(3,2)(.78)^2 (.22)^1   = .402

Here's my "seat of the pants" answer

We should remove 5

Reason :  Every other number can be paired with another number to give a sum of 10....5 cannot be paired with any other number to give a sum of 10

Hectictar has answered the first one here :

https://web2.0calc.com/questions/please-help-ty_3

P ( Red and Blue).....no chance of this.....if we draw one marble...it can't be both red and blue 

So

P( R and B)  =   0

First one   -  3

Second one  - 2

Third one  - 1

GREAT JOB, RP    !!!!

Second one

We have 13 cards

P ( 5  or D )  = P(5) + P(D)  - P  (5 and D)

                        2/13  +  7/13  -   1/13

                              8/13

Last one

P ( A or B)  =   P(A)  +  P (B)  -  P (A  ∩ B)

                  =     8/45  + 11/45  -  2/45            

                  =     17/45

P(B or C)  =   P(B)  + P(C)  - P(B  ∩C)

                  = 11/45 + 10/45  - 1/45

                 =  20/45

P (C or D)  = P(C)  + P (D)  - P (C  ∩ D)

                  =  10/45  + 12/45  - 0/45

                  =   22/45

Call the original price of the goods, P

After a 30% discount   the price is .7P

And...after a 20% discount on this the final price is  (.7P) (.8)  = .56P

So...the discount  is just [ P  -.56P]  = .44P

And the merchant's claimed discount is .50P

So....the difference between the true discount and merchant's claimed discount  is

l  .44P - .50P  l   =  l  -.06P l  =   .06P   =  [ 6 %  of the original price ]