EXAMPLE 1 Direct Variation During a thunderstorm you see the lightning before you hear the thunder because light travels much faster than sound. The distance between you and the storm varies directly as the time interval between the lightning and the thunder. (a) Suppose that the thunder from a storm 5400 ft away takes 5 s to reach you. Determine the constant of proportionality, and write the equation for the variation. (b) Sketch the graph of this equation. What does the constant of proportionality represent? (c) If the time interval between the lightning and thunder is now 8 s, how far away is the storm?

デジタル形式で段階的に解決 ありがとう!! SOLVE STEP BY STEP IN DIGITAL FORMAT A steel bar is taken out of a furnace at a temperature of 900 °C and allowed to quench in air for 60 minutes, reaching a temperature of 50 °C. If the environment is at 20 °C and the rate of change of the temperature of the bar with respect to time is proportional to the temperature difference between the bar and the environment, determine: a) the proportionality constant b) the time it takes for the steel bar to reach 35 °C