1. What is the natural number comes exactly in the middle between 5 and 15?
Your Answer:
[Correct Answer]:10
Hint:
1) 15 − 5 = 10. 2) Half of 10 is 5. 3) The answer then can be obtained by either (5 + 5) or (15 − 5).
Example 2.
2. Anne has 9 different pairs of socks in a drawer. How many socks will she need to take out from the drawer in order to make sure to find a pair of socks??
Your Answer:
[Correct Answer]:10
Hint:
Counting the extreme case before having a pair. 9 + 1
Example 3.
3. There are 8 red balls and 12 green balls in a bag. At most how many balls do you need to pick from the bag in order to make sure that you have balls of different colors?
Your Answer:
[Correct Answer]:13
Hint:
Consider the extreme case when picked all green balls before picking the first red ball.
Example 4.
4. How many knots are needed to make in order to connect 12 short strings into one long string?
Your Answer:
[Correct Answer]:11
Hint:
Starts with two short strings.
Example 5.
5. A group of students lined up. Counting from left to right, Hillary is the 4th in line; counting from right to left, Hillary is the 3rd. How many students are there in total?