Problem 1 Two friends played chess for three hours. For how long did each of them play?
Answer Each of them played for three hours. !
Problem 2 A cart driven by three horses in one harness made 15 miles in 2 hours. What was the average speed of a single horse in the harness?
Answer The average speed of each horse was 7.5 mph. !
Problem 3 A train from Boston to New York departs exactly at 12 PM. An average speed of this train is 45 mph. At the same time the second train departs from New York to Boston. An average speed of the second train is 65 ml/hr. When the trains pass each other somewhere midway, which one is closer to Boston?
Answer Both trains are at the same distance to Boston at the meeting point. !
Problem 4 John and Mary Smith have five sons. Each of the sons has one sister. How many children are there in the family?
Answer Six. John and Mary Smith have five sons and one daughter. !
Problem 5 A carpenter has to saw each of 15 logs into 6 equal parts. How many saw cuts should be done?
Answer Seventy five. In order to saw one log into 6 equal parts a carpenter has to do five saw cuts. !
Problem 6 It takes the elevator 30 seconds to get to the 6 th floor. How long would it take to get to the 2 nd floor on the same elevator?
Answer Six seconds. It takes five times longer to get to the 6 th floor than to the 2 nd floor. !
Problem 7 In order to buy a book John has to pay $10 plus one half of the books price. How much does the book cost?
Answer The book costs $20. !
Problem 8 Peter wrote a legitimate expression: – 45 = – 54. Then he rewrites it as 5 * (7 + 2 – 9) = 6 * ( ). Then he noticed equal expressions in parentheses and reduced both parts by this expression. He got 5 = 6. Where did he make a mistake?
Answer (7+2-9)=0 Peter cannot reduce both parts by 0. !
Problem 9 Is it possible to have five weekends in one month?
Answer Of course, it is possible. For example : The 1 st weekend falls on the 1 st and the 2 d days of the month; The 2 d weekend falls on the 8 th and the 9 th days of the month; The 3 d weekend falls on the 15 st and the 16 d days of the month; The 4 th weekend falls on the 22 d and the 23 d days of the month; The 5 th weekend falls on the 29 th and the 30 th days of the month. !
Problem 10 Harry said: The day before yesterday I was 10 years old. The next year I will celebrate my 13 th birthday. Is it possible? If so, when is Harrys birthday?
Answer Yes, it is possible, but only if Harrys birthday is December 31 st. !