Lateral Thinking Watch
You have a noughts and crosses grid. You arrange the numbers 1-9 in the boxes. Then multiply all the adjacent numbers (not diagonally adjacent, just vertically and horizontally). add up all of your answers. The maximum possible is 377. see if you can get it.
Also try this - not so much of a puzzle unless you intend on explaining it.
Take a three digit number where all digits are different. Write the number backwards so you now have two separate numbers. Take the smaller away from the bigger. You now have a new number. If your new number is two digits put a zero in front of it. write it backwards so you have two numbers again. Add them and you'll be interested to know the answer will be 1089.