related rates word problems

[rmsbu]

If two resistors with resistances R₁ and R₂ are connected in parallel, as in the figure below, then the total resistance R, measured in ohms (Ω), is given by

1

R

=

1

R1

+

1

R2

.

If R₁ and R₂ are increasing at rates of 0.3 Ω/s and 0.2 Ω/s, respectively, how fast is R changing when R₁ = 100 Ω and R₂ = 110 Ω?

 

[Ishuda]

...If R₁ and R₂ are increasing at rates of 0.3 Ω/s and 0.2 Ω/s, respectively, how fast is R changing when R₁ = 100 Ω and R₂ = 110 Ω?

When you say R₁ is increasing at rates of 0.3 Ω/s, the formula for R₁ becomes
R₁ = R₁₀ + 0.3 t
where t is in seconds. Similarly for R₂
R₂ = R₂₀ + 0.2 t
So, given that
(\(\displaystyle \frac{1}{F}\))' = \(\displaystyle \frac{-F'}{F^2}\)
and
\(\displaystyle \frac{1}{R}\) = \(\displaystyle \frac{1}{R_1}\) + \(\displaystyle \frac{1}{R_2}\)
what is R' when R₁ = 100\(\displaystyle \Omega\) and R₂ = 110\(\displaystyle \Omega\)

Edit: Not thinking clearly - made a bad assumption and had to delete it.