Question

1. problem: join all 9 dots using only 4 straight lines, without taking your pencil off the paper? you cannot go over any line twice.

Explanation:

Step1: Start from top - left dot

Draw a line diagonally down - right through 3 dots.

Step2: Extend the line

Extend the line beyond the bottom - right dot.

Step3: Turn and draw

Turn and draw a line diagonally up - left through 3 dots.

Step4: Finish with a line

Draw a horizontal line through the remaining 3 dots.

Answer:

It is possible by thinking outside the box (extending lines beyond the square formed by the dots).