3.3 O timization Problems 7. A box with an open top is to be constructed from a rectangular piece of cardboard, 2m by 3m , by cutting out a square from each of the four corners and bending up the sides. Find the dimensions of the box corresponding to a maximum volume. in: 8. Find the dimensions of the largest right-cylinder that can be inscribed in a cone of radius R = 6m and height H =9m . 3.3 Optimization Problems 9. A north-south road intersects an east-west road at a point 0 . A motorcycle crosses 0 . at noon, travelling West at a constant speed of 80 kmfh . At the same time, a car is 50m South of 0 , travelling North at 601mm. Find the time at which they are closest to each other, and approximate the minimum distance between them. 10. The sum of two non-negative numbers is 16. Find the maximum possible value and the minimum possible value of the sum of their cube roots. 3.4 Optimization Problems in Economics and Science 1. A farmer wants to fence an area of 96001112 in a rectangular eld and divide it in hall with a fence parallel to one of the sides of the rectangle. Find the dimensions (length and width) of the rectangular field that minimize the cost of the fence? 2. The selling price (in $) of an item is p(x) = 60 0.021: , where x is the number of items sold per day. If the cost (in $) of manufacturing x items is c(x) = 1000 +10x, find the number of items to be manufactured per day in order to maximize the profit. 3.4 OEtimization Problems in Economics and Science 3. The cost (in $) of manufacturing x thousands units of USB memory sticks is given by C(17): 21::2 50x + 800 . How many items must be produced in order to minimize the unit cost u(x) = c(x)l x. 4. A farmer wishes to fence in a rectangular field of 60,000 m2 . The North and the South fences cost 152nt while the East and the West fences cost $31' m . Find the dimensions of the field that will minimize the cost. 3.4 Optimization Problems in Economics and Science 5. A closed box with a square base is to contain 2520113 . The bottom costs $5! cm2 , the top costs $2107:2 , and the sides cost ass/cm2 . Find the dimensions that will minimize the cost. 6. A soda cracker package (the top is closed) is to be constructed in the shape of a rectangular prism with a square base. The total capacity is 512 cm3 . Find dimensions (length, width, and height) that will minimize the cost. 3.4 Optimization Problems in Economics and Science 7. A cylindrical can (the top is closed) is to be made to hold 10006m3 of oil. Find the dimensions (radius and height) of the can that will minimize the cost of the metal to make the can. 3. Corn silos are usually in the shape of a cylinder (with a closed base) surmounted by a hemisphere. lithe volume of a silo is 10003113, what dimensions (radius and height) of the silo would use the minimum amount of materials? 3.4 Optimization Problems in Economics and Science 9. A tank has hemispherical ends and a cylinder center. The cost (per square meter} of manufacturing the hemispherical ends is double in comparison with the cost (per square meter) of manufacturing the cylindrical part. Find the proportions (the ratio between height and radius) of the cylinder that will maximize the volume for a given total cost. 10. A lifeguard can run on the beach at Sm! s and swim at 4 ml 3. If an incident happens at 40 m from the shore and the lifeguard is on the shore at lOOmfrom the incident place, find the minimum amount of time it takes for the liteguard to reach the place where the incident has occurred