1. Equations & Inequalities

In Exercises 11–20, write an equation that expresses each relationship. Then solve the equation for y.x varies jointly as y and z.

Use the four-step procedure for solving variation problems given on page 447 to solve Exercises 1–10.y varies jointly as a and b and inversely as the square root of c. y = 12 when a = 3, b = 2, and c = 25. Find y when a = 5, b = 3 and c = 9.

Use the four-step procedure for solving variation problems given on page 447 to solve Exercises 1–10.y varies jointly as x and z. y = 25 when x = 2 and z = 5. Find y when x = 8 and z = 12.

Use the four-step procedure for solving variation problems given on page 447 to solve Exercises 1–10.y varies directly as x and inversely as the square of z. y = 20 when x = 50 and z = 5. Find y when x = 3 and z = 6.

Use the four-step procedure for solving variation problems given on page 447 to solve Exercises 1–10.y varies inversely as x. y = 12 when x = 5. Find y when x = 2.

Solve the variation problems in Exercises 77–82. The pitch of a musical tone varies inversely as its wavelength. A tone has a pitch of 660 vibrations per second and a wavelength of 1.6 feet. What is the pitch of a tone that has a wavelength of 2.4 feet?

Solve the variation problems in Exercises 77–82. The distance that a body falls from rest is directly proportional to the square of the time of the fall. If skydivers fall 144 feet in 3 seconds, how far will they fall in 10 seconds?

Write each formula as an English phrase using the word varies or proportional. C=2πr, where C is the circumference of a circle of radius r.

Write each formula as an English phrase using the word varies or proportional. r = d/t, where r is the speed when traveling d miles in t hours.

Write each formula as an English phrase using the word varies or proportional. V = 1/3 πr^2h, where V is the volume of a cone of radius r and height h

Solve each problem. Circumference of a CircleThe circumference of a circle varies directly as the radius. A circle with radius 7 in. has circumference 43.96 in. Find the circumference of the circle if the radius changes to 11 in.

Solve each problem. Resistance of a WireThe resistance in ohms of a platinum wire temperature sensor varies directly as the temperature in kelvins (K). If the resistance is 646 ohms at a temperature of 190 K, find the resistance at a temperature of 250 K.

Solve each problem. Distance to the HorizonThe distance that a person can see to the horizon on a clear day from a point above the surface of Earth varies directly as the square root of the height at that point. If a person 144 m above the surface of Earth can see 18 km to the horizon, how far can a person see to the horizon from a point 64 m above the surface?

Fill in the blank(s) to correctly complete each sentence, or answer the question as appropriate.In the equation y = 6x, y varies directly as x. When x=5, y=30. What is the value of y when x=10?

Using k as the constant of variation, write a variation equation for each situation. h varies inversely as t.