Answer:
a - 13/30
Step-by-step explanation:
2/5 +x = 5/6
2/5 + x -2/5 = 5/6 - 2/5
x = 13/30
Answer:

Step-by-step explanation:

After removing one black marble:

Answer:The object will hit the ground after 5 seconds
Step-by-step explanation:
Given height of tower =80 ft
h=-16
+64t+80
When the object will hit the ground its height=0
0=-16
+64t+80
Multiplying both sides by -1
16t²-64t-80=0
Dividing by 16 both sides
t²-4t-5=0
(t-5)(t+1)=0
t=5 or -1
So t=5 since time cannot be negative
The object will fall after 5 seconds
Answer:
No this is a not good experimental design
Step-by-step explanation:
In an experiment, we seek to establish cause an effect relationship. The effect of one variable on another is examined while keeping other variables constant. A control often establishes the validity of the experiment.
Now the ten rubber bands were selected at random from each box. The experimental group was put in a freezer while the control group was maintained at room temperature.
Comparison of the mean stretch before breakage of the rubber bands in both groups establishes the effect of cold temperature on elasticity of rubber bands.
However, this is not a good experimental design because the sample rubber bands should have been picked from different boxes of brand A and B and not from the same box.
Secondly, samples from the two brands should have been put in the freezer and kept at room temperature. That is, ten rubber bands from A are put on the freezer and another 10 are left at room temperature. 10 rubber bands from B are put in the freezer and another 10 are left at room temperature.
The mean elasticity of the both groups can now be meaningfully compared from the data obtained.