Answer:
1/25
Step-by-step explanation:
At the start there is a 4/20 (1/5) chance of drawing a blue marble. After putting the marble back in the bag, there is again a 1/5 chance of drawing a blue marble again. To calculate the overall probability, you must multiply the two numbers together: 1/5 x 1/5 = 1/25.
There are 24 permutations.
The number of permutations of 4 objects taken 4 at a time is given by
4!/(4-4)! = 4!/0! = 4!/1 = 4! = 24
P = 2(L + W)
P = 80
W = 1/3L
80 = 2(L + 1/3L)
80 = 2(3/3L + 1/3L)
80 = 2(4/3L)
80 = 8/3L
80 * 3/8 = L
240/8 = L
30 = L .... length (L) is 30 ft
W = 1/3L
W = 1/3(30)
W = 30/3
W = 10 <== width (W) = 10 ft
