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jarptica [38.1K]
3 years ago
11

A person of height 1.6m up to the eye level is standing at a point 2m away from the bank of the river and found an angle of elev

ation of 30°. find the width of the river.​
Mathematics
1 answer:
natima [27]3 years ago
5 0

Step-by-step explanation:

tan30° = Height of person / (Distance away from river bank + river's width) = 1/√3.

Therefore 1.6m / (2m + x) = 1/√3

By cross multiplication, 1.6√3 = 2 + x.

Hence, x ≈ 0.77m.

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A large fish tank at an aquarium needs to be emptied so that it can be cleaned. When its
VikaD [51]

Answer:

The draining time when only the big drain is opened is 2.303 hours.

The draining time when only the small drain is opened is 5.303 hours.

Step-by-step explanation:

From Physics, we know that volume flow rate (\dot V), measured in liters per hour, is directly proportional to draining time (t), measured in hours. That is:

\dot V \propto \frac{1}{t}

\dot V = \frac{k}{t} (Eq. 1)

Where k is the proportionality constant, measured in liters.

From statement, we have the following three expressions:

(i) <em>Large and small drains are opened</em>

\dot V_{s}+\dot V_{l} = \frac{k}{2} (Eq. 2)

\frac{\dot V_{s}+\dot V_{l}}{k} = \frac{1}{2}

(ii) <em>Only the small drain is opened</em>

\dot V_{s} = \frac{k}{t_{l}+3} (Eq. 3)

\frac{\dot V_{s}}{k} = \frac{1}{t_{l}+3}

(iii) <em>Only the big drain is opened</em>

\dot V_{l} = \frac{k}{t_{l}} (Eq. 4)

\frac{\dot V_{l}}{k}  = \frac{1}{t_{l}}

By applying (Eqs. 3, 4) in (Eq. 2) and making some algebraic handling, we find that:

\frac{1}{t_{l}+3}+\frac{1}{t_{l}} = \frac{1}{2}

\frac{t_{l}+t_{l}+3}{t_{l}\cdot (t_{l}+3)} = \frac{1}{2}

2\cdot t_{l}+3 = t_{l}^{2}+3\cdot t_{l}

t_{l}^{2}-t_{l}-3 = 0 (Eq. 5)

Whose roots are determined by the Quadratic Formula:

t_{l,1}\approx 2.303\,h and t_{l,2} \approx -1.302\,h

Only the first roots offers a solution that is physically reasonable. Hence, the draining time when only the big drain is opened is 2.303 hours. And the time needed for the small drain is calculated by the following formula:

t_{s} = 2.303\,h+3\,h

t_{s} = 5.303\,h

The draining time when only the small drain is opened is 5.303 hours.

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3 years ago
What is 2(3a+2b-7) equivalent too?
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Answer:

6a+4b-14

Step-by-step explanation:

For this, we have to use the distributive property.

This means we multiply each value in the parentheses by 2.

2*3a=6a

2*2b=4b

2*(-7)=-14

So our equation is:

6a+4b-14

8 0
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What is 11/3 divided by 2/3
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Answer:

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Step-by-step explanation:

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2 years ago
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