WASHINGTON STATE MATHEMATICS COUNCIL
1999 MIDDLE SCHOOL MATH OLYMPIAD
SIXTH GRADE NUMBER SENSE
(Make sure you include the units in your answer!)

6

1. How many 3-digit numbers between 100 and 1000 have a 4 as the middle digit?

 

 

 

2. The sum of 4 consecutive (in a row) numbers is 50. What is the smallest of these numbers?

 

 

 

3. A mad scientist discovers a new microbe that grows at a fantastic rate. The number of microbes doubles every hour. In 12 hours these microbes covered a whole petri dish. After how many hours did the microbes cover half the petri dish?

 

 

 

4. What is the least common multiple of 12 and 26?

 

 

 

5. The number 45n78 is divisible by 3. What is the sum of all possible values of n?