1. A father can do a job as fast as two sons working
together. If one son does the job alone in 3 hours and the other does it alone in 6 hours, how many hours does it take the father to do the job alone?
2. Ten minutes after a plane leaves the airport, it is reported that the plane is 40 miles away. What is the average speed of the plane, in miles per hour?
3. One machine can do a given task in 15 hours, and a newer model can do it in 5 hours less. If both machines work simultaneously（同时）, in how many hours will the job be completed?
4. If 10 men can do a piece of work in 20 days, how long will it take 8 men to do the job if they work at the same rate?
5. A graduating class of 356 votes to choose a
president（班长）. With 5 candidates seeking office（谋职）, what is the least number of votes a successful candidate could receive and yet have more votes than any other candidate?
6. A dry cleaner offers a 20% discount（打折）on all dry cleaning done during a special period. If the regular cost of dry cleaning a rug（小地毯）is $2.25, how much will be the cost of cleaning this rug during this period?
7. A contractor（承包人）estimates that he can paint a house in 5 days using 6 men. If he actually uses only 5 men for the job how many days will it take to do this job?
8. Village A has a population of 6,800, which is decreasing at a rate of 120 per year. Village B has a population of 4,200, which is increasing at a rate of 80 per year. In how many years will the population of the two villages be equal?
9. Two cars start towards each other from points 200 miles apart. One car travels at 40 miles an hour and the other travels at 35 miles an hour. How far apart will the two cars be after four hours of continuous traveling?
10. The distance between two cities is 1,800 miles. How many gallons of gasoline will a motorist use with an automobile that uses (on the average) 1 gallon of gasoline for each 12 miles？
11. A man travels for 5 hours at an average rate of
12. A 64-pound mixture of sand and gravel（砾石）is 25% sand. How many pounds of sand must be added to produce to a mixture that is 40% gravel?
Solution to the Intelligence Test
1. 2 hours 2.
5. 72 votes 6. $1,80 7. 6 days 8. 13 years
9. 100 miles 10. 150 gallons 11.
12. 56 pounds of sand
