(20 ) the dot plot below shows the amount of time two random groups of students took to brush their teeth: based on visual inspection of the dot plots, which of the following groups, if any, shows a greater average time required to brush their teeth? group r group s both groups show about the same average time. no conclusion about average time can be made from the data.

The correct option is C.

Step-by-step explanation:

In a dot plot, the number of dots above a number represents the frequency of that number.

From the given dot plot it is clear that number of dots for group R is 21 and the time taken by the students of groups R are

45, 50, 50, 55, 60, 60, 70, 75, 80, 85, 90, 90, 95, 100, 100, 105, 110, 110, 115, 120, 120

The average of the data is

From the given dot plot it is clear that number of dots for group S is 17 and the time taken by the students of groups S are

50, 55, 60, 60, 65, 70, 70, 80, 90, 90, 95, 100, 105, 110, 110, 115, 120

The average time of both groups are same.

Since both groups show about the same average time, therefore the correct option is C.

x = -3

y = -18

step-by-step explanation:

to solve by substitution, substitute one variable and solve for the other. then substitute again to find the remaining variable.

x-1/3(3x-9) = -3 since y=3x-9 substittute y.

x-1/3(3x-9)=-3

x + x +3 = -3

2x+3=-3

2x+3-3= -3-3

2x=-6

x=-3

substitute again into y=3x-9

y=3(-3)-9

y=-9-9

y=-18

answer is (b.

164 ft2)

a base  

18

b base  

7

h height  

8