Coliform bacteria are distributed in a river at an average concentration of 1 per 20 cc of water. If we draw from the river a test tube containing 10cc of water, what is the probability that the sample contains exactly 2 coliform bacteria

0.5

Step-by-step explanation:

Given that: An average concentration of 1 coliform bacteria per 20 cc of the river water.

This implies that in 20 cc of the water, it is certain that 1 coliform bacteria would be found. So that:

pr(1 bacteria in 20 cc of water) = 1

i.e the probability of getting 1 bacteria in 20 cc of water is 1.

The probability of the 10 cc sample of water containing 2 coliform bacteria can be determined as:

pr(2 bacteria in 10 cc of water) =

                                                   = 0.5

7 ft 6 in means 7 1/2, because 6 in is 1/2 of a foot. 7 ft 8 in means 7 2/3 because 8 in is 2/3 of a foot. 23/3 = 7 2/3. 15/2 = 7 1/2.

23/3   *   15/2   = 57 1/2

step-by-step explanation:

{x = -1/2 ,   y = -1

step-by-step explanation:

solve the following system:

{2 x + y = -2

{10 x - 3 y = -2

in the first equation, look to solve for y:

{2 x + y = -2

{10 x - 3 y = -2

subtract 2 x from both sides:

{y = -2 x - 2

{10 x - 3 y = -2

substitute y = -2 x - 2 into the second equation:

{y = -2 x - 2

{10 x - 3 (-2 x - 2) = -2

10 x - 3 (-2 x - 2) = (6 x + 6) + 10 x = 16 x + 6:

{y = -2 x - 2

{16 x + 6 = -2

in the second equation, look to solve for x:

{y = -2 x - 2

{16 x + 6 = -2

subtract 6 from both sides:

{y = -2 x - 2

{16 x = -8

divide both sides by 16:

{y = -2 x - 2

{x = -1/2

substitute x = -1/2 into the first equation:

{y = -1

{x = -1/2

collect results in alphabetical order:

answer:   {x = -1/2 ,   y = -1