ElectricPavlov

volume_cylinder  = pi r^2 h            r = 7 m    h = 9  

25 in    +   2 in/wk *  7 wk   =       ......   in

After w  weeks     25   +   2 * w

45 coins

n

d = n+1

q= 3n-1         summed = 45 coins

n      +    n+1      +    3n-1        = 45        solve for 'n'  the number of nickles

I think the expected value would be    3 x 1/10   = .3      there are 8 of these   = .24

                                                            9 x 1/10  = .9        there are 2 of these = 1.8         sum = 4.2

  (8x 3 + 2 x 9 ) / 10 = 4.2

now add a '9' piece of paper        3 x 1/11 x 8 = 2.1818

                                                     9 x 1/11 x 3 = 2.4545                sum = 4.63

[(8x3)+(3x9)]/11 = 4.63

Sorry....back up a bit..... ball can only be launched from numbered area......so  12   is correct  ......I missed it !   Ball cannot be launched from 'D'.

Now calculate the diagonal of the little squares.....

I think you are missing the point.......you should understand HOW the answer was derived.....not just LOOK FOR THE ANSWER.....

    but you got what you wanted......

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Start at D.....then what do you count?

First calculate the length of the diagonal of the squares.....

    then start at each point and follow the path (counting the squares crossed)  the ball would follow before hitting a corner

        once you find the longest path......multiply the number of diagonals x the length of the diagonal...

             I found  .........    as the longest path.....what do YOU find ?

1/j   +  1/n   =  1/5

1/j  +  1/12   = 1/5     solve for 'j'   jenny's time alone

1/j = 1/5 - 1/12

1/j = 7/60

j = 60/7 hr

  = 8.57 hr     = 8 hr 34 min