Math Olympiad 4

Number Sense ( Week 16 Evaluation)

1. What is the natural number comes exactly in the middle between 6 and 12?

2. 433 is a 3-digit number with each digit less than or equal to the digits in higher place values, i.e 3 ≤ 4 and 3 ≤ 3. How many such 3-digit number(s) are there between 250 and 299 inclusively?

3. If the odometer of a car reads 39,268 miles, what is the next odometer reading with at least four digits that are the same?

4. What is the greatest common factor (GCF) of 42 and 22?

5. In the product 15 × 16 × 17 × 18 × 19 × 20 × 21, which one of the seven numbers should be reduced by 1 to cause the smallest decrease in the product?

6. In the number sequence below, there is a number which is special. What is it?
18, 27, 36, 45, 54, 57.

7. What positive integers are equal to their rightest digit squared?

8. Using all the numbers of 5, 8, 9, 11, 14 and +, +, −, × operators, can an even number and an odd number be produced respectfully?

Yes No

9. Which of the following statements is correct?

A) A large negative integer is not necessarily less than a small positive integer

B) To add an integer is the same as to subtract the opposite of the integer

C) The further left a negative integer is from zero, the larger its value

D) The sum of two positive integers is not necessarily positive

10. Make a 5 using the following 5 numbers: 5, 7, 9, 10 and 4. You can use +,-,*,/, and ( ) as many times as you wish, but you need to use all 5 numbers and each number only once.