Is this a direct proportion?

y=2x

Which statement best describes an inverse proportion relationship between y and x?

6 men can paint a building in 15 days. Find the number of days taken for 5 men to paint the same building.

Determine the type of variation

$$y=\frac{k}{x^2}$$  

Determine the type of variation:

What type of proportion does the table represent?

Write a direct proportion equation.

Y is directly proportional to the square of z and inversely proportional to w.

Write a direct proportion equation for the graph

The interest received on a savings account varies directly with the amount deposited. Daniel received $55.35 in interest on $1230 he deposited. How much interest would Daniel have received if he had deposited $2000 into his account?

If 8 men can assemble 28 cars in one day, how many cars can 20 men assemble in one day?

Ten identical pipes turned on simultaneously can fill a swimming pool in 9 hours. How long will it take 6 pipes to fill the same swimming pool?

The distance that an automobile travels varies directly as the time it travels. If the car travels 280 miles in 7 hours, how far will it travel in 12 hours?

Which of the given graphs is a direct proportion?

The number of hours to paint a house varies inversely with the number of painters working. A 2400-square foot house can be painted in 27 hours by 6 painters. How many painters would need to work in order to paint the house in 18 hours?

What type of variation does this scenario represent?
The length of time you charge your cell phone
and the battery power 

The width of a rectangle varies inversely with its length. if the width is 4 when the length is 18, find the width when the length is 8.

The amount of money spent at the gas station varies directly with the number of gallons purchased. When 9.5 gallons of gas were purchased the cost was $36.52. How much would 12 gallons of gas cost?

The number of pencils sold varies directly as the cost. If 5 pencils cost $0.45, find the cost of 7 pencils.