How do you find $f(20)$ , if $f(x)$ varies inversely with $x$ and $f(12)=5$ ?

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Answer 1 · 2018-05-10T09:19:23

$f(20)=3$

As $f(x)$ varies inversely as $x$ , we have $f(x)=k*1/x$

and as $f(12)=5$ , we have $k*1/12=5$ i.e. $k=12xx5=60$

Hence $f(x)=60*1/x=60/x$

and $f(20)=60/20=3$

How do you find f(20)f(20), if f(x)f(x) varies inversely with xx and f(12)=5f(12)=5?