1. The information given in the problem is:
- <span>The length of a rectangular garden is 8 feet longer than the width.
- </span><span>The garden is surrounded by a 4-foot sidewalk.
- The area of the sidewalk is 320 ft</span>².
2. So, the length of the rectangular garden is:
L1=8+W1
3. The formula for calculate the area of the sidewalk, is:
A2=L2xW2
"A2" is the area of the sidewalk (A2=320 ft²).
"L2" is the length of the sidewalk.
"W2" is the widht of the sidewalk.
4. The length of the sidewalk (L2) is:
L2=L1+4+4 (4 feet on each side)
L2=L1+8
5. When you substitute L1=8+W1 into the equation L2=L1+8, you obtain:
L2=8+W1+8
L2=W1+16
6. The widht of the sidewalk is:
W2=W1+4+4
W2=W1+8
7. Now, you must substitute the length and the widht of the sidewalk into the formula A2=L2xW2:
A2=L2xW2
A2=(W1+16)(W1+8)
320=W1²+16W1+8W1+128
W1²+16W1+8W1+128-320=0
W1²+16W1+8W1-192=0
8. When you solve the quadratic equation, you obtain the value of W1:
W1=16.97 ft
9. Finally, you must substitute the value of W1 into the formula L1=8+W1:
L1=8+W1
L1=8+16.97
L1=24.97 ft
10. Therefore, the dimensions of the garden are:
L1=24.97 ft
W1=16.97 ft
Let's compare apples to apples and oranges to oranges: convert each given proper fraction into its decimal counterpart:
3 63/80 => 3 .788 approx.
3 1/5 => 3.2
3 11/20 => 3.55
It's now an easy matter to arrange these numbers from least to greatest:
3.2, 3.55, 3.79, or
3 1/5, 3 11/20, 3 63/80
<span>a) Differentiate both sides of lnq − 3lnp + 0.003p=7 with respect to p, keeping in mind that q is a function of p and so using the Chain Rule to differentiate any functions of q:
(1/q)(dq/dp) − 3/p + 0.003 = 0
dq/dp = (3/p − 0.003)q.
So E(p) = dq/dp (p/q) = (3/p − 0.003)(q)(p/q) = (3/p − 0.003)p = 3 − 0.003p.
b) The revenue is pq.
Note that (d/dp) of pq = q + p dq/dp = q[1 + dq/dp (p/q)] = q(1 + E(p)), which is zero when E(p) = −1. Therefore, to maximize revenue, set E(p) = −1:
3 − 0.003p = −1
0.003p = 4
p = 4/0.003 = 4000/3 = 1333.33</span>
