Problem of the Week #17

Grade 6:
Fill in the blank fields by writing either 2, 5, or 10 into them so that the sum of the numbers in each column and each row is 22.
___ 2 ___ ___
___ ___ ___ 5
5 ___ ___ ___
10 ___ ___ 5

Grade 7:
Break up 60 into the sum of two numbers so that one seventh of one of the numbers is the same as one eighth of the other number.


Grade 8:
I have only $10 and $20 bills in my pocket. There are three times as many $20 bills than $10 bills. I have a total of $490. How many $20 bills do I have?


Grade 9:
A man had $10 000 to invest. He invested $4000 at 5 percent and $3500 at 4%, simple annual interest. In order to have a yearly interest income of $500, at what rate must he invest the remainder of his money?

Grade 10:
The shortest side of a right triangle is 7 cm, and its smallest angle is 15 degrees. How long is its hypotenuse?