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Varvara68 [4.7K]
3 years ago
13

z varies directly with x and inversely with y^2. When x = 2 and y = 5, z = 8. What is the value of z when x = 4 and y = 9?

Mathematics
2 answers:
Ivanshal [37]3 years ago
4 0
Direct variation is  y = kx

Inverse variation is y = k/y

if z varies directly with x, then the equation would be z = kx

if z varies inversely with y^2 then the equation would be z = k/y^2. Combining, these two, we have z = kx/y^2

We use the first set of values to find the constant k:

x = 2, y = 5, z = 8:

8 = 2x/25, k = 100. Now we use the second set of values to find z:

x = 4, y = 9, k = 100 and z is unknown:

z = (4X100)/9^2

z = 400/81--> this is your final final answer.

*plz rate brainliest
Kaylis [27]3 years ago
3 0

The Answer is definitely..

400/81

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nadya68 [22]
Speed = Distance / Time
Distance = Speed*Time

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for upstream, the boat goes against the current, and so its speed is

U = V - C

where V is the speed of the boat
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for downstream, it will be:

D = V + C

Convert the problem into mathematical equations:

4D + 3U = 116
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4(V+C) + 3(V-C) = 116
4V + 4C + 3V -3C =116
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3(V+C) + 4(V-C) = 108
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Solving the equations:

7V + C = 116
7V - C = 108

14V = 224
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to get C:
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dsp73

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