1I w 1. Write the formula that expresses the relationship described 2. c varies directly as a 3. w varies inversely as x 4. r varies directly as the square of s 5. j is inversely proportional to the cube of m Find the constant of variation and write the formula to express the relationship using that constant 6. c varies inversely as d and c = 7 when d = 4 7. t varies directly as the square of u and t = 6 when u = 3 8. w is inversely proportional to the cube of x and w is 54 when x = 3 9. h is directly proportional to j and h = 12 when j = 8 Solve each of the following variation problems by setting up a formula to express the relationship, finding the constant, and then answering the question. 10. Hooke's law states that the distance that a spring is stretched by hanging object varies directly as the mass of the object. If the distance is 20 cm when the mass is 3 kg, what is the distance when the mass is 5 kg? 1 1. The time required to drive a fixed distance varies inversely as the speed. It takes 5 hr at a speed of 80 km/h to drive a fixed distance. How long will it take to drive the same distance at a speed of 70 km/h? 12. The intensity of illumination falling on a surface from a given source of light is inversely proportional to the square of the distance from the source of light. The unit for measuring the intensity of illumination is usually the footcandle. If a given source of light gives an illumination of 1 foot-candle at a distance of 10 feet, what would the illumination be from the same source at a distance of 20 feet