Answer:
It is the 2nd choice!
Step-by-step explanation:
Answer: A) 45 ft
Step-by-step
The yardstick is 3ft tall since 1 yard = 3ft. It is 3 times as tall as its shadow. The tree has a 15ft long shadow. The tree should also be 3 times as tall as its shadow. The tree is 15*3ft tall, so it is 45ft tall. I attached an image of the diagram I made.
Current density of solution a/m2 is given below
Step-by-step explanation:
Current density is the measure of current generated per unit surface area of electrode.
Eg: In microbial fuel cell/fuel cells, if you are using electrode with size of 5cm x 2cm and current produced is 200mA, then current density will be,
CD= Current/(projected area of electrode)
area of rectangle= LxB= 5cm x 2cm =10cm2
CD= 200mA/10cm2
CD= 20mA/cm2
Your Current will be 200mA.
Current density will be 20mA/cm2.
X=pounds of coffee bean ($0.20 per pound)
y=pounds of coffee bean ($0.68 per pound )
We can suggest this system of equations:
x+y=120
(0.20x+0.68 y) / (x+y)=0.54 ⇒ (0.2x+0.68y)=0.54(x+y)
We can solve this system by substitution method.
x+y=120 ⇒ y=120-x
0.2x+0.68(120-x)=0.54[x+(120-x)]
0.2x+81.6-0.68x=0.54(120)
-0.48x+81.6=64.8
-0.48x=64.8-81.6
-0.48x=-16.8
x=-16.8/-0.48
x=35
y=120-x=120-35=85
Answer: the coffee mixture has 35 pounds of coffee beans sold to $0.2 a pound, and 85 pounds of coffee beans sold to $0.68 a pound, the solutions is reasonable because the price of a coffee mixture ($0.54 a pound) is greater than $0.2 and smaller than $0.68.
