Tham khảo tài liệu 'math word problem demystified phần 7', ngoại ngữ, anh ngữ phổ thông phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | LESSON 16 Solving Lever Problems 5. Let X the distance from the fulcrum where Tina should sit. I fK L 4- ỊL2L2 W 4- WjJi 72 12 90 8 96x 4-80 12 864 4- 720 96x 4- 960 1584 96x4-960 1584 - 960 96x 4- 960 - 960 624 96x 624_P61x 96 X Tina should sit feet from the fulcrum. LESSON Solving Work Problems Work problems involve people doing a job. For example if Frank can cut a lawn in 2 hours and his younger brother can cut the same lawn in 3 hours how long will it take them to cut the grass if they both work together In this case we have two people doing the same job at the same time but at different rates. Another type of problem involves pipes filling or draining bodies of water such as tanks reservoirs or swimming pools at different rates. For example if one pipe can fill a large tank in 5 hours and a smaller pipe can fill the tank in 3 hours how long would it take to fill the tank if both pipes are turned on at the same time Again we have two pipes doing the same job at different rates. The basic principle is that the amount of work done by one person machine or pipe plus the amount of work done by the second person machine or pipe is equal to the total amount of work done in a given specific LESSON 17 Solving Work Problems time. Also the amount of work done by a single person machine or pipe is equal to the rate times the time that is Rate X Time Amount of work done EXAMPLE Frank can cut a lawn in 2 hours. His brother Jeff can cut the same lawn in 3 hours. How long will it take them if they cut the lawn at the samé time SOLUTION GOAL You are being asked to find the time in hours it will take both boys to cut the grass if they work together. STRATEGY Let x the time it takes them if they work together. Now in one hour Frank can cut I of the lawn and Jeff can cut I of the lawn. Rate X Time Amount of work done Frank Ị 2 X 1 2X Jeff 1 3 X 1 3X Frank does Ịx or amount of work and Jeff does or ị amount of work. These are the fractional parts of work done by each. .
