x |
6 |
12 |
18 |
24 |
30 |
36 |
42 |

y |
120 |
60 |
40 |
30 |
24 |
20 |
120/7 |

a)What variation model does this table represent?

direct variation

inverse variation

b)What is the model that relates y and x?

y=720x

y=720x^{2}

y=720/x

y=720/x^{2}

As x increases, y is decreasing, so we know that the table represents an inverse variation model. In this case, the model is y=k/x (also, xy=k) where k is easily calculated using simple algebra. K=720; therefore, the model is y=720/x.