The time to complete a standardized exam is approximately normal with a mean of 70 minutes and a standard deviation of 10 minus. using the 68-95-99.7 rule, what percentage of students will complete the exam in under an hour?

Step-by-step explanation:

Given that the  time to complete a standardized exam is approximately normal with a mean of 70 minutes and a standard deviation of 10 minutes.

P(completing exam before 1 hour)

= P(less than an hour) = P(X<60)

=P(Z<)

=0.5-0.34=0.16

i.e. 16% of students completed the standardized exam.

8(-10x+3.5y-7)

8×-10x + 8×3.5y + 8×-7

-80x + 28y - 56

therefore

-80x+28y-56 is the correct answer