Chapter 1 - Equations and Inequalities - 1.5 Applications and Modeling with Quadratic Equations - 1.5 Exercises - Page 132: 40

$1hr 1min$

Step 1. Assume they can talk $x\ hr$. Step 2. The leg dimensions of the right triangle formed after this time are: $2.5x$ and $3x$ Step 3. They will reach the limit when the hypotenuse is $4\ mi$, use Pythagorean Theorem, we have: $(2.5x)^2+(3x)^2=4^2$ or $15.25x^2=16$ Step 4. Take the positive solution from above, we have $x\approx1.0243\ hr \approx 1hr 1min$