The length of time needed to complete a certain test is normally distributed with mean 92 minutes and standard deviation 8 minutes. Find the probability that it will take less than 80 minutes to complete the test.

The probability that it will take less than 80 minutes

  P(X≤80) = 0.0768        

Step-by-step explanation:

Step(i):-

Given mean of the Population = 92 minutes

Given standard deviation of the Population = 8 minutes

Let 'X' be the random variable in normal distribution

Let 'X' = 80 minutes

Step(ii):-

The probability that it will take less than 80 minutes

P(X≤80) = P(Z≤-1.5)

            =  0.5 - A(1.5)

            = 0.5 - 0.4232

           =0.0768

Final -

The probability that it will take less than 80 minutes

  P(X≤80) = 0.0768        

step-by-step explanation:

equation

you are asked to write the equation

  expression = 0

using the given expression. when you do that, you have

  2x^2-2x-12 = 0

factoring

you can see that each of the coefficients is even, so a factor of 2 can be removed immediately.

  2(x^2 -x -6) = 0

if you multiply the binomials (x+a)(x+b), you get

  (x +a)(x +b) = x^2 +(a+b)x +ab

this tells you the coefficient of x is the sum of two factors of the constant term. here, that means -1 is the sum of two factors of -6. we want to know those factors so we can factor the trinomial.

  -6 = -1×6 = -2×3 = -3×2 = -6×1

the factor pair that sums to -1 is {-3, 2}, so our factorization is

  2(x -3)(x +2) = 0

solutions

the solutions to this equation are the values of x that make the product zero. a product is zero only when only of the factors of the product is zero. here, that means

  x - 3 = 0

  x = 3 . . . add 3 to both sides of the equation

or

  x +2 = 0

  x = -2 . . . add -2 to both sides of the equation

the solutions to the equation are x=3 or x=-2. both of these values of x satisfy the equation—they make it be true.

∠acb = 8°

step-by-step explanation:

∠xba lies on the circle and is half the measure of the intercepted arc ax

hence

measure of arc ax = 2 × 42° = 84°

∠acb is outside the circle and is

∠acb = (arcab - arcax ), hence

∠acb = 0.5 (100 - 84) = 0.5 × 16° = 8°