Follow the Rules for Working with Measurements $\frac { 1 } { R } = \frac { 1 } { R _ { 1 } } + \frac { 1 } { R _ { 2 } } + \frac { 1 } { R _ { 3 } }$

Follow the rules for working with measurements.
Use the formula $\frac { 1 } { R } = \frac { 1 } { R _ { 1 } } + \frac { 1 } { R _ { 2 } } + \frac { 1 } { R _ { 3 } }$ .
Given $R _ { 1 } = 78 \Omega$ , $R _ { 2 } = 60 \Omega$ and $R _ { 3 } = 78 \Omega$ , find R. Give the answer to one decimal place.
R = __________Ω