Understanding Direct and Inverse Variation

What is the equation that represents a direct variation between two variables?

In a direct variation, if Y = 28 when X = 7, what is the constant of proportionality?

Using the direct variation equation Y = 4X, what is Y when X = 3.5?

According to Hook's Law, if a spring stretches 12 cm with a 4 kg mass, what is the constant of proportionality?

In Hook's Law, if the constant of proportionality is 3, what is the displacement when the mass is 5 kg?

What is the equation that represents an inverse variation between two variables?

In an inverse variation, if Y = 27 when X = 1/3, what is the constant of proportionality?

Using the inverse variation equation Y = 9/X, what is Y when X = 18?

If a pump empties a tank in 45 minutes at 300 gallons per minute, what is the constant of proportionality?

Using the inverse variation equation T = 13,500/R, how long will it take to empty the tank at 500 gallons per minute?