\f18. '7 At current growth rates, the Earth's popu- lation is doubling about every 69 years. If this growth rate were to continue, about how many years will it take for the Earth's population to become one-fourth larger than the current level? \f24. For a 14-inch pizza, find the area of a slice with angle = radians.32. What is the slope of the radius of the unit circle that has a 60 angle with the positive horizon- tal axis? 6. Find two points on the horizontal axis whose distance from {1, 4) equals 6