Acivil engineer is analyzing the compressive strength of concrete. compressive strength is approximately normally distributed with variance σ 2 = 1000 psi2 . a random sample of 12 specimens has a mean compressive strength of ¯x = 3255.42 psi. (a) test the hypothesis that mean compressive strength is 3500 psi. use a fixed-level test with α = 0.01.

The radius of the base of a cylinder is 10 centimeters, and its height is 20 centimeters. a cone is used to fill the cylinder with water. the radius of the cone's base is 5 centimeters, and its height is 10 centimeters.

The function a represents the cost of manufacturing product a, in hundreds of dollars, and the function b represents the cost of manufacturing product b, in hundreds of dollars. a(t) = 5t + 2 b(t) = 7t - 2t +4 find the expression that describes the total cost of manufacturing both products, a(t) + b(t). a. 7t^2 - 7t + 2 b. 7t^2 + 3 +6 c. 7t^2 + 7t - 6 d. 7t^2 - 3t + 6

Ineed with number 6 , explain how to get 1978