Answer:
The amount of oil was decreasing at 69300 barrels, yearly
Step-by-step explanation:
Given


Required
At what rate did oil decrease when 600000 barrels remain
To do this, we make use of the following notations
t = Time
A = Amount left in the well
So:

Where k represents the constant of proportionality

Multiply both sides by dt/A


Integrate both sides


Make A, the subject

i.e. At initial
So, we have:






Substitute
in 

To solve for k;

i.e.

So:

Divide both sides by 1000000

Take natural logarithm (ln) of both sides


Solve for k



Recall that:

Where
= Rate
So, when

The rate is:


<em>Hence, the amount of oil was decreasing at 69300 barrels, yearly</em>
The reference angle is a positive acute angle. Angle 7π/6 in radians= = 7*180°/6 = 210° ( because π rad=180°).
This angle is in the 3rd Quadrant and formula for the reference angle is:
x-180°.
210°-180°=30°
Answer: The reference angle for 7π/6 is 30°.
Let the width be X
Then the length is X + 70
The perimeter is the sum of all sides
There are 2 widths (left side and right side) and 2 lengths (top and bottom)
Perimeter = 2 * width + 2 * length
Perimeter = 2 * X + 2 * (X+70)
Perimeter: 2 X + 2 X + 140 = 380
4 X = 380-140
4 X = 240
X = 240 / 4
X = 60
Width = 60 - the smaller of two sides
Length = X + 70 = 60 + 70 = 130 - the larger of two sides
Check:
<span>
2 * 60 + 2 * 130 = 380 </span>
Answer:
42
Step-by-step explanation:
Answer:
c 15
Step-by-step explanation:
Tangent AB is tangent to circle D at point A. The angle made by a tangent to a circle and a radius of the circle at the point of tangency is a right angle. That means that angle is a right angle, and triangle ABD is a right triangle.
We can use the Pythagoren theorem.
a^2 + b^2 = c^2
x^2 + 20^2 = (x + 10)^2
x^2 + 400 = (x + 10)(x + 10)
x^2 + 400 = x^2 + 10x + 10x + 100
400 = 20x + 100
20x = 300
x = 15