Question: It is your friend's birthday tomorrow, and you are planning a surprise party for them. For this party, you got perfectly spherical balloons and you are filling these balloons with helium. The helium enters that balloon at a rate of 70cm3/s (i.e. the volume of the balloon is increasing at this rate). How quickly is the radius of the balloon change when the diameter of the balloon is 55cm? Please show your steps.

Answer: dr/dt = ________________ cm/s