Question

my teacher did the inverse of 1/10+1/20 and got 6.67 as an answer. will someone please explain to me how they did it?

Answer 1

$\begin{gathered} \frac{1}{10}+\frac{1}{20}=\frac{1\times20+1\times10}{10\times20} \\ =\frac{30}{200} \\ =\frac{3}{20} \end{gathered}$

To find the invers of the expression 1/10+1/20, divide 1 with the above expression.

$\begin{gathered} Inverse\text{ of (}\frac{1}{10}+\frac{1}{20}\text{)}=\text{Inverse of (}\frac{3}{20}\text{)} \\ =\frac{1}{\frac{3}{20}} \\ =1\times\frac{20}{3} \\ =6.67 \end{gathered}$

Thus, the inverse of the given expression is 6.67.