Choose the equation that expresses that F is directly proportional to t. Symbols a , b , c , d are constants.

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1. F = at

2. F = ct 3 + d

3. F = b

Express the statement “M varies directly as x and inversely as y” as a formula. Use the information that if x = -36 and y = 9 then M = -16 to find the constant of proportionality. Select the correct answer:

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1. 4

2. -16

3. -12

The cost of a sheet of gold foil is proportional to its area. If a rectangular sheet measuring 14 cm by 12 costs $33.60, how much would a 2 cm by 4 cm sheet cost? Select the correct answer:

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1. $1.60

2. $1.28

3. $3.20

4. $0.80

The heat experienced by a hiker at a campfire is proportional to the amount of wood on the fire, and inversely proportional to the cube of his distance from the fire. If he is 22 ft from the fire, and someone doubles the amount of wood burning, how far from the fire would he have to be so that he feels the same heat as before? Select the correct answer:

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1. 27.72 ft

2. 33 ft

3. 44 ft