The area <em>A</em> of a trapezoid with height <em>h</em> and bases <em>b</em>₁ and <em>b</em>₂ is equal to the average of the bases times the height:
<em>A</em> = (<em>b</em>₁ + <em>b</em>₂) <em>h</em> / 2
We're given <em>A</em> = 864, <em>h</em> = 24, and one of the bases has length 30, so
864 = (<em>b</em>₁ + 30) 24 / 2
864 = (<em>b</em>₁ + 30) 12
864 = (<em>b</em>₁ + 30) 12
72 = <em>b</em>₁ + 30
<em>b</em>₁ = 42
Let P be Brandon's starting point and Q be the point directly across the river from P.
<span>Now let R be the point where Brandon swims to on the opposite shore, and let </span>
<span>QR = x. Then he will swim a distance of sqrt(50^2 + x^2) meters and then run </span>
<span>a distance of (300 - x) meters. Since time = distance/speed, the time of travel T is </span>
<span>T = (1/2)*sqrt(2500 + x^2) + (1/6)*(300 - x). Now differentiate with respect to x: </span>
<span>dT/dx = (1/4)*(2500 + x^2)^(-1/2) *(2x) - (1/6). Now to find the critical points set </span>
<span>dT/dx = 0, which will be the case when </span>
<span>(x/2) / sqrt(2500 + x^2) = 1/6 ----> </span>
<span>3x = sqrt(2500 + x^2) ----> </span>
<span>9x^2 = 2500 + x^2 ----> 8x^2 = 2500 ---> x^2 = 625/2 ---> x = (25/2)*sqrt(2) m, </span>
<span>which is about 17.7 m downstream from Q. </span>
<span>Now d/dx(dT/dx) = 1250/(2500 + x^2) > 0 for x = 17.7, so by the second derivative </span>
<span>test the time of travel, T, is minimized at x = (25/2)*sqrt(2) m. So to find the </span>
<span>minimum travel time just plug this value of x into to equation for T: </span>
<span>T(x) = (1/2)*sqrt(2500 + x^2) + (1/6)*(300 - x) ----> </span>
<span>T((25/2)*sqrt(2)) = (1/2)*(sqrt(2500 + (625/2)) + (1/6)*(300 - (25/2)*sqrt(2)) = 73.57 s.</span><span>
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</span><span>mind blown</span>
823 × 43 = 35389
anything to ask please pm me
Answer:
21 calories per cup
Step-by-step explanation:
4cups↔84calories
1cup ↔less
1/4x84=21calories
Answer:
22years
Step-by-step explanation:
The sum of ages of people in the room is 40 * 5= 200
[ Remember mean = total ahead of people/ number of people]
Let the age of the 6th person be X
200+x. / 6 = 37
200 + x = 37 * 6 = 222
x = 222- 200 = 22
