### Substitution Cipher

Find the frequency distribution for ordinary English, and use it to help you crack the code.

### Secret Transmissions

How can Agent X transmit data on a faulty line and be sure that her message will get through?

### Secondary Cipher Challenge Part 1

Here is the start of a six-part challenge. Can you get to the end and crack the final message?

# The Best Card Trick?

##### Stage: 3 and 4 Challenge Level:

James, from Hampton School, gave us his ideas on how to order the cards to show to his partner:

For the first set of 5 cards, the two cards with the same suit are the diamonds: the 4d should be the "base" card as the gap between the 4d and the 6d is 2, which can be expressed using the remaining three cards with l h m. Therefore, from right to left, the cards would be the 4 of diamonds followed by the 5 of clubs, the 10 of spades and the 9 of hearts, allowing you to guess the 6 of diamonds.

Jamie and Monty from Hurstpierpoint Prep School came to the same conclusion.

Aswaath, from Garden International School, Kuala Lumpur, sent us his thoughts on how he would show his partner the cards:

For the first set of cards, I would place four cards in this particular order: 4d, 5c, 10s and 9h. I would keep 6d the secret card.

For the second set of cards, I would place four cards in this particular order: Qh, 8d, 10s and 2c. I would keep 3h the secret card.

For the third set of cards, I would place four cards in this particular order: 7h, 7s, 7d and 7c. I would keep Kh the secret card.

Great - you all seem to have understood Charlie's crib sheet well!