Have I done this correctly?

f is inversely proportional to d

when d=50, f=256

Find value of f when d=80

Figured out a constant of 25/125

so

f=50/1*125/25=250

Is thsi correct?

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- May 31st 2010, 09:14 AMMukilabInversely proportional
Have I done this correctly?

f is inversely proportional to d

when d=50, f=256

Find value of f when d=80

Figured out a constant of 25/125

so

f=50/1*125/25=250

Is thsi correct? - May 31st 2010, 09:23 AMnikhil
its incorrect

since f is inversely proportional to d we have

f=k/d where k is a constant

now as f=256 when d=50 then

k=fd=50*256

so value of f when d=80

f=(50*256)/80=160 - May 31st 2010, 09:23 AMskeeter
f is inversely proportional to d ...

$\displaystyle f = \frac{k}{d}$

... where k is the constant of proportionality.

substitute in the given values to solve for k ...

$\displaystyle 256 = \frac{k}{50}$

$\displaystyle k = 50 \cdot 256 = 12800

$

$\displaystyle f = \frac{12800}{d}$

... finish the problem - May 31st 2010, 09:30 AMMukilab
ah I did d/k.

Thanks.