Chapter 13 - Partial Derivatives - 13.1 Functions Of Two Or More Variables - Exercises Set 13.1 - Page 914: 11

The answer is below.

$(a)$ $v=7$ lies between $v=5$ and $v=15$ $5+2=7=\frac{2}{10}+5$ $W C I \approx 19+\left[\frac{2}{10}\right](13-19)=19-1.2=17.8^{\circ} \mathrm{F}$ (b) $T=28$ lies between $T=25$ and $T=30$ $28=25+\sqrt{\frac{3}{5}}(30-25),$ so $W C I \approx \left[\frac{3}{5}\right](25-19)+19=3.6+19=22.6^{\circ} \mathrm{F}$