Answer:
D is answer. So if we do -2 * 3 we get -6, -6-4 = -10. Well that doesn't work for a because its 10 not -10. But we have spotted something already. We do have -2 and -10. Those two work we just tested it, but A doesn't work. The only pair that has the -2 and -10 is d. Sorry for bad english, its not native language
<h2><u>
Answer: D</u></h2>
<span>solution:
we have, mean =8.4 hrs, std. deviation = 1.8 hrs, sample size n = 40 , X = 8.9
Probability(X<8.9) = ?
we know that, Z = (X - mean)/(std. deviation/(sqrt. n)) = (8.9 - 8.4)/(1.8/(sqrt.40))
Z = 1.7568
from standard normal probabilities table, we have , P(Z<1.7568) = 0.9608
Hence, probability that the mean rebuild time is less than 8.9 hours is 0.9608</span>
