Problem of the Week # 23: April 7th 2008

Grade 6:
Jill went to the school store and bought the following items;
4 pencils for $0.23 each, 2 pens for $0.59 each, one notebook for $0.90 and a binder for $2.50. There was not tax on these items. Jill paid with a $10 bill. How much change did she get back?

Grade 7:

Find five Prime numbers that add to make 43 for a total. Arrange them in order from smallest to largest and give the Median of the five numbers.

Grad 8:
Determine the smallest positive integer that consists of different digits, all of which are even, that is also a multiple of 9?

Grade 9:
If the mean of twenty different positive integers is 20, what would be the greatest possible value of any one of these twenty numbers?

Grade 10:
A Mathematician noticed that the numbers 992 and 578 have a special property: the sum of the digits of each number is equal to 20. ( 9 + 9 + 2 = 20 and 5 + 7 + 8 = 20)
How many other three digit numbers have this property?