1. My son is five times as old as my daughter, and my wife is five times as old as my son. I am twice as old as my wife, and my grandmother, who is as old as all of us put together, is 81 years old today. How old is my son?
2. There are 13 steps in Surmaiya's staircase. One step squeaks every time someone steps on it. Last week, one friend started on step 1 and climbed to the top taking 2 steps at a time. A second friend started from the floor and climbed to step 13 by taking 3 steps up and 1 down. Even though Surmaiya was listening carefully, she heard no squeak either time. Which step is squeaky?
3. Ben signed a contract that says he must build 10 doghouses for the SPCA. The organization wants them ready within one month. For every doghouse that Ben completes, he will receive $40; for every one that he fails to complete, he will be fined $10. At the end of the month, Ben received $150. How many doghouses did he build?
5. The 756 high school students in the survey in 'Cell Phones and landlines' were sophmores, juniors, and seniors. The number of sophmores in the survey is one-half the number of seniors. The number of juniors in the survey is twice the number of seniors. How many sophmores participated in the survey?
4. Joe has a certain number of dimes in his pocket. If the dimes were pennies, he would have $1.08 less than he has now. How many dimes does he have in his pocket?
6. A can with 40 marbles in it weighed 135 grams. The same can with 20 marbles weighed 75 grams. What is the mass of each marble? What is the mass of the can?