Step 3 We are given that the length is increasing at a rate of 4 cm/s and the width is increasing at a rate of 9 cm/s. Therefore, we have the following. dl = 9 dt X dw = 8 dt X Furthermore, we are given that the length is 8 cm when the width is 6 cm. In other words, when = 8, we have the following. W=9 x