What is 12 times the square root of 16?
1 answer:
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Answer:
84 feet
Step-by-step explanation:
This problem involves several steps. The first step is to realize that the given figure does not show the required number of vertical stringers. It shows 5, but there will be 7 of them. The given diagram is helpful in that it shows a vertical stringer on the centerline of the arches.
The second step is to write a function that will tell you how long the stringer will be. I find it convenient to write the equation for an arch shape such as this using the parent function h(x) = 1-x^2. This parent function gives an arch of height 1 and width 1 from center (a total width of 2). You want an arch that is 16 ft high and 40 ft wide (one side from center), so you must scale this parent function both horizontally (by 40) and vertically (by 16). It becomes ...
H(x) = 16(1 -(x/40)^2)
The taller arch is twice this height, so the length of a vertical stringer at position x is
vertical length = 2H(x) -H(x) = H(x)
That is, the function H(x) we defined can be used to find the length of the stringers.
The third step is to find the stringer lengths. It can save some energy if you realize that the problem is symmetrical, so that the stringer at x=-30 is the same length as the one at x=30. We need to find stringer lengths every 10 feet from -40 feet to +40 feet. Of course, the ones at ±40 feet are zero length, because that is where the two arches meet.
H(-30) = 16(1 -(3/4)^2) = 7
H(-20) = 16(1 -(1/2)^2) = 12
H(-10) = 16(1 -(1/4)^2) = 15
H(0) = 16
Then the fourth step is to add up the stringer lengths, rounding the result as required.
7 +12 +15 +16 +15 +12 +7 = 16 + 2(34) = 84 . . . . feet (no rounding needed)
Finally, you need to answer the question asked:
The sum of vertical stringer lengths is 84 feet.
Answer: (9, 10800)
Step-by-step explanation:
We will first let x be the number of years and y be the total cost.
In that case, let's plug in the values for each into the equation <em>y=mx+b, </em>where m is the slope and b is the y-intercept.
The y-intercept will be the <u>value we start with before any years pass</u>, so it will be the <u>installation cost</u>. The slope is <u>how fast the total cost will increase</u>. Since the <u>operation costs</u> have to be added on every year, it will be our slope.
With that in mind, let's create both of our equations:
- y = 900x + 2700 (Oil system)
- y = 200x + 9000 (Solar system)
Since y is solved for in the first equation, we can substitute it into the second equation:
<em>[Subtracting 200x from both sides]</em>
<em /> <em>[Subtracting 2700 from both sides]</em>
<em /> <em>[Dividing both sides by 700]</em>
<em />
We can now substitute 9 for x in any equation and solve for y. Here I substituted it into the first one:
<em>[Multiplying]</em>
<em /> <em>[Adding]</em>
Hence, the solution to this linear system is (9, 10800).