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### Grade 8 - Mathematics2.9 Compound Proportion

 Example: 10 men can lay a road 75 Km. long in 5 days. In how many days can 15 men lay a road 45 Km. long. Solution: Let x be number of days. Ratio of days = 5:x. Number of men is inversely proportional to number of days. So inverse of ratio of men = 15:10 = 3:2. Length of road is directly proportional to number of days. Therefore, Ratio of lengths = 75:45 = 5:3 5:x = 3*5:2*3 x*3*5 = 5*2*3 x = (5*2*3)/(3*5) x = 2. Number of days required = 2 days. Directions: Solve the following problems. Also write at least ten examples of your own.
 Q 1: The dorm charges \$6300, for 35 students for 24 days , in how many days will the dorm charges be \$3375 for 25 students.15 days16 days17 days18 days Q 2: 175 men can dig a canal 3150m. long in 36 days. How many men are required to dig a canal 3900m. long in 24 days.330 men325 men315 men320 men Question 3: This question is available to subscribers only! Question 4: This question is available to subscribers only!