High-strength concrete is supposed to have a compressive strength greater than 6,000 pounds per square inch (psi). a certain type of concrete has a mean compressive strength of 7,000 psi, but due to variability in the mixing process it has a standard deviation of 420 psi, assuming a normal distribution.

Answer

given,

greater compressive strength = 6,000 psi

mean compressive strength(μ) = 7000 psi

standard deviation (σ) = 420 psi

P(X < 6000)                                              

Z = - 2.38                    

P(Z<-2.38) = Area to left - 2.38

from Z table                          

P(X < 6000) = P(Z<-2.38) = 0.0087

P(fail) = P(X< 6000) = 0.0087 = 0.87

15

step-by-step explanation:

we are given the following expression and we are to solve it and find the product:

-13 × (-5)

solving the given expression in the standard order of solving a mathematical expression, beginning with the opening of brackets and then multiplying the terms and changing their signs.

-3 × -5 = 15 (answer is positive because when negative is multiplied with negative, it gives a positive answer)

0.16 or 16%

step-by-step explanation:

lets take a coin for example.

if you toss it twice, it has a 1/4 chance of landing on heads both times because 1/2 * 1/2 is 1/4.

with the cards, the chance of picking dog is 0.4. having two people pick one is like picking a card twice in a row. so 0.4 * 0.4 is 0.16, or 16%