Graphical Reasoning Logic Judgment Definition Judgment Analogy Reasoning
When answering questions about the relationship between the number of tests, the special value method will appear in my mind from time to time. "Can I set a 100 question to make the method simpler?" Application of special value method in it.
Method 1: When multiple working hours for completing a job are known, let the total work amount be the least common multiple of the working time.
Example 1. Four engineering teams A, B, C, and D build a road. A and B cooperation can be completed in 8 days, and A, C, or B and D cooperation can be completed in 7 days. Asking C and D cooperation can be better than A and B. How many days before the cooperation is completed?
Method 2: When the working efficiency ratio is known, set the ratio to the working efficiency.
Example 2. The work done by A in one day is equal to the work done in B for two days, and the work done in C for 3 days. The existing project can be completed in 2 days. Q How long does it take for B and C to work together?
A. 12 days B. 5 days C. 2.4 days D. 10 days
[Answer] C. Analysis by the public: From the question, we can know that the working efficiency ratio of A, B, and C is 6: 3: 2, and the working efficiency of A, B, and C can be set to 6, 3, and 2, respectively, so the total work is 6 × 2 ﹦ 12. It takes 12 ÷ (3 + 2) ﹦ 2.4 days for B and C to cooperate. Choose option C.
Method three: When multi-labor cooperation, set the workload per person or item per unit time to 1.
Example 3. To build a highway, assuming that everyone has the same daily work efficiency, 180 workers are planned to be completed in 1 year. After 4 months of work, due to special circumstances, it is required to complete the task 2 months in advance. How many workers do you need to add?
A.50 B.65 C.70 D.60
[Answer] D. Zhong Gong analysis: If the workload of each person is 1 for a month, the total workload is 180 × 12, 4 months have been worked, and the remaining workload is 180 × (12-4) ﹦ 180 × 8, which requires 2 months in advance When finished, there are only 6 months left to work, and the amount of work to be completed each month is 180 × 8 ÷ 6 ﹦ 240, which means 240 workers, so it is necessary to increase 240-180 ﹦ 60, and choose option D.
Through the above three questions, I believe that the students have a corresponding understanding of using special value method to solve engineering problems. Through follow-up exercises, Zhong Gong Education believes that everyone can learn from these questions.
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