Chapter 1, Equations and Graphs - Section 1.10 - Modeling Variation - 1.10 Exercises - Page 165: 40

$L=1305.61$ lb

Since $L$ varies jointly as the square of the speed $s$ and the area $A$, we have: $L=ks^{2}A$ We are given: $L=1700$ and $s=50$ and $A=500$, so we have: $1700=k*50^{2}*500$ $ k=0.00136$ Therefore: $L=0.00136s^{2}A$ We plug in $A=600$ and $s=40$ to find $L$: $L=0.00136*40^{2}*600=1305.61$ lb