Exploring and noticing

An examination paper is made from five pieces of paper. What is the sum of the other page numbers that appear on the same sheet as page 5?

One year there were exactly four Tuesdays and four Fridays in October. On what day of the week was Halloween.

By drawing 5 horizontal and four vertical lines, one can form 12 rectangles. What is the greatest number of rectangles that can be formed by drawing 15 lines?

Weekly Problem 51 - 2016
Pegs numbered 1 to 50 are placed in a row. Alternate pegs are knocked down, and this process is repeated. What is the number of the last peg to be knocked down?

Five numbers added together in pairs produce: 0, 2, 4, 4, 6, 8, 9, 11, 13, 15 What are the five numbers?

What are the possible dimensions of a rectangular hallway if the number of tiles around the perimeter is exactly half the total number of tiles?

Use the numbers in the box below to make the base of a top-heavy pyramid whose top number is 200.

Weekly Problem 24 - 2012
Can you put these very close fractions into order?

How many 10-digit numbers containing only 1s, 2s and 3s can you write?

Can you solve the clues to find out who's who on the friendship graph?