You may also like

Mind Reading

Think of a number, add one, double it, take away 3, add the number you first thought of, add 7, divide by 3 and take away the number you first thought of. You should now be left with 2. How do I know?

How Many Miles to Go?

How many more miles must the car travel before the numbers on the milometer and the trip meter contain the same digits in the same order?

Summing Consecutive Numbers

15 = 7 + 8 and 10 = 1 + 2 + 3 + 4. Can you say which numbers can be expressed as the sum of two or more consecutive integers?

Card Trick 1

Age 11 to 14 Challenge Level:

Try this card trick, it is mathematical. Can you explain (using mathematics) how it works? You might like to consider using some symbolism.

Here are the instructions:

Volunteer chooses 20 cards in the pack to turn face up.

Volunteer then shuffles the pack.

Volunteer removes the top twenty cards without me looking and the remainder are laid on the table.

The twenty cards are handed back to me, without me looking:

I dont know how many cards are reversed in this group I am holding, but it is likely to be less than the number in the rest of the pack. I like things to be balanced so I am going to try to turn some of the cards over so that both piles have the same number face up.


Turn the whole group upside down.

Count out the number which are face up in each pile. (they should both be the same!)