Question 116980
Fungicides account for one tenth of the pesticides used in the United States.
 Insecticides account for one fourth of all the pesticides used in the United
States. The ratio of fungicides to insecticides used in the United States can be
 written as one tenth divided by one fourth. Write this ratio in simplest form.
:
Here's what it says:
{{{1/10}}} / {{{1/4}}}
When you divide fractions you:
"Invert the dividing fraction and multiply"
{{{1/10}}} * {{{4/1}}} = {{{4/10}}} = {{{2/5}}}
:
:
The combined resistance of two resistors R1 and R2 in a parallel circuit is
 given by the formula RT = 1 over 1r1 + 1r2. Simplify the formula.
:
I think you mean:
Rt = {{{1/((1/r1) + (1/r2))}}} 
:
Change the denominator portion to be a single fraction over a common denominator
{{{((1/r1) + (1/r2))}}} = {{{(r2 + r1)/(r1*r2)}}}
:
This is divided into 1 which just consists of inverting the dividing fraction, so we have;
{{{(r1*r2)/(r2 + r1)}}}; the old "product over sum" formula for two resistors in parallell
:
:
Did this help you find your way, somewhat?