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Anvisha [2.4K]
3 years ago
14

I need help on this one!!

Mathematics
2 answers:
Vedmedyk [2.9K]3 years ago
6 0

We know 15 minutes contain 15*60 = 900 seconds, the time for 85 blinks

Then the time for each blink t = 900/85

Time elapsed in seconds for 51 blinks is then 51*t = 900*51/85 = 540 seconds

romanna [79]3 years ago
4 0

As the answer wants to know the seconds, find the seconds. 15 * 60 = 900. We know he blinks 85 times in 900 seconds, so divide 900 by 85 to find the rate at which George blinks. 900 / 85 = 10.588. Multiply 10.588 by 51 to find the number of seconds for 51 blinks. 51 * 10.588 = 539.988.

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How to find the shaded region of a circle with a rectangle inside?
WINSTONCH [101]
You would start by finding the area of the circle and then finding the area of the rectangle. After finding both, subtract the area of the rectangle from that of the circle. <span />
8 0
4 years ago
Joe bought 5 apples and 4 bananas for $6. Dawn bought 3 apples and 6 bananas for $6.30. How much foes each apple and each banana
zepelin [54]

Answer:

Apple = $0.6

Banana = $0.75

Step-by-step explanation:

Let us represent Apple by A and Banana by B

For Joe,

5A + 4B = 6       (1)

For Dawn

3A + 6B = 6.3     (2)

To eliminate A, Multiply equation (1) by 3 and equation (2) by 5

15A + 12B = 18          (3)

15A + 30B = 31.5       (4)

subtracting equation (4) from (3)

15A - 15A +12B - 30B = 18 - 31.5

-18B = -13.5

divide through by -18

-18B/-18 = -13.5/-18

B = 0.75

substitute 0.75 in equation (1)

5A + 4B = 6

5A + 4(0.75) = 6

5A + 3 = 6

subtract 3 from both sides

5A + 3 - 3 = 6 - 3

5A = 3

divide through by 5

5A/5 = 3/5

A = 0.6

4 0
3 years ago
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3 years ago
You are a lifeguard and spot a drowning child 60 meters along the shore and 40 meters from the shore to the child. You run along
sukhopar [10]

Answer:

The lifeguard should run across the shore a distance of 48.074 m before jumpng into the water in order to minimize the time to reach the child.

Step-by-step explanation:

This is a problem of optimization.

We have to minimize the time it takes for the lifeguard to reach the child.

The time can be calculated by dividing the distance by the speed for each section.

The distance in the shore and in the water depends on when the lifeguard gets in the water. We use the variable x to model this, as seen in the picture attached.

Then, the distance in the shore is d_b=x and the distance swimming can be calculated using the Pithagorean theorem:

d_s^2=(60-x)^2+40^2=60^2-120x+x^2+40^2=x^2-120x+5200\\\\d_s=\sqrt{x^2-120x+5200}

Then, the time (speed divided by distance) is:

t=d_b/v_b+d_s/v_s\\\\t=x/4+\sqrt{x^2-120x+5200}/1.1

To optimize this function we have to derive and equal to zero:

\dfrac{dt}{dx}=\dfrac{1}{4}+\dfrac{1}{1.1}(\dfrac{1}{2})\dfrac{2x-120}{\sqrt{x^2-120x+5200}} \\\\\\\dfrac{dt}{dx}=\dfrac{1}{4} +\dfrac{1}{1.1} \dfrac{x-60}{\sqrt{x^2-120x+5200}} =0\\\\\\  \dfrac{x-60}{\sqrt{x^2-120x+5200}} =\dfrac{1.1}{4}=\dfrac{2}{7}\\\\\\ x-60=\dfrac{2}{7}\sqrt{x^2-120x+5200}\\\\\\(x-60)^2=\dfrac{2^2}{7^2}(x^2-120x+5200)\\\\\\(x-60)^2=\dfrac{4}{49}[(x-60)^2+40^2]\\\\\\(1-4/49)(x-60)^2=4*40^2/49=6400/49\\\\(45/49)(x-60)^2=6400/49\\\\45(x-60)^2=6400\\\\

x

As d_b=x, the lifeguard should run across the shore a distance of 48.074 m before jumpng into the water in order to minimize the time to reach the child.

7 0
3 years ago
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