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y varies jointly as a and b, and inversely as the square root of c. y = 24 when a = 6, b = 2,and c=4. Find y when a = 3, b=5, and c= 25.y=

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We have an unknown quantity, which is y. We are told that it varies joint as a and b. This translates as follows


y=k\cdot a\cdot\text{b }

where k is a constant.

Now, we are also told that it varies inversely as the square root of c. So this look as follows


y=\frac{k}{\sqrt[]{c}}

where k is another constant. We have to combine both facts as follows


y=\frac{k\cdot a\cdot b}{\sqrt[]{c}}

in this case, k is a constant. Now, we are told that whenever c=4, b=2 and a=6 we get y=24. So we get the following equation


24=\frac{k\cdot6\cdot2}{\sqrt[]{4}}=(k\cdot6\cdot2)/(2)=6\cdot k

By dividing by 6 on both sides, we get


k=(24)/(6)=4

So the general expression of y looks like this


y=\frac{4\cdot a\cdot b}{\sqrt[]{c}}

Now, we want to calculate the value of y whenever a=3 and b=5 and c=25. So we get


y=\frac{4\cdot3\cdot5}{\sqrt[]{25}}=(4\cdot3\cdot5)/(5)=4\cdot3=12

so y=12 whenever a=3, b=5 and c=25.

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