Answer is •D because of the seburation
Answer:
to the shop : 5/8 of an hour
back home : 3/8 of an hour
Step-by-step explanation:
We use the relationship between distance travelled, speed and time given by the formula:
speed = distance / time
We know that the distance from home to the coffee shop is D (same for trip back)
We also know the two speeds in one direction 9 mph and in the other 15 mph
then we can find the times t1 (to the coffee shop) and back (t2) by using the equations:
D = 9 * t1
D = 15 * t2
1 = t1 + t2
We set the two distances equal to have:
9 * t1 = 15 * t2
then t1 = 15 * t2 / 9 = 5 t2 / 3
and use this to substitute for t1 in the last equation:
t1 + t2 = 5 t2/3 + t2 = 1
8 t2 /3 = 1
then t2 = 3/8 of an hour
and therefore t1 must be 1 - t2 = 5/8 of an hour
Answer:
3/12 is less than 3/4
Step-by-step explanation:
3/12 is the same as 1/4, which is 0.25
3/4 is 0.75
Answer:
Variance of difference between pre-exam and post-exam grades = 10.8
Step-by-step explanation:
Correlation (X,Y) = Covariance (X,Y) / √ { Variance (X) . Variance (Y) }
Given : Correlation (Pre & post exam grade) = 0.9 ; Variance (Pre exam grade) = 0.90 ; Variance (Post exam grade) = 16
So, 0.9 = Covariance (X,Y) / √ { 16 x 9 }
0.9 = Covariance (X,Y) / 12
Covariance (X,Y) = 12 x 0.9 = 10.8