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The Caesar cipher – practice for Years 5–7

Sample questions on The Caesar cipher with the right answer and a worked solution, from easy to hard. In the Pickles Academy app a child gets new questions of the same kind every time, so they can't just learn the answers by heart.

Subject
Computing
Year
Years 5–7
Curriculum area
Data, information and modelling

Question types: Shifting letters

Rule: The Caesar cipher

To encrypt, move every letter the same number of places on in the alphabet; to decrypt, move it back.

After Z the alphabet starts again at A.

Example: Shift 3: H → K, E → H, L → O, O → R, so HELLO → KHOOR. Also X → A, Z → C.

Watch out: To decrypt, shift backwards: KHOOR with shift 3 is HELLO, not NKRRU.

Sample questions

  1. Question 1 Easy

    The Caesar cipher moves every letter the same number of places on in the alphabet (after the last letter comes the first again). Alphabet: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z. Encrypt the word MOON with a shift of 1.

    1. A) OQQP
    2. B) PRRQ
    3. C) NPPO
    4. D) OPPN
    5. E) LNNM
    Show the solution
    Answer: C) NPPO

    How it works: M→N, O→P, O→P, N→O

  2. Question 2 Normal

    The Caesar cipher moves every letter the same number of places on in the alphabet (after the last letter comes the first again). Alphabet: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z. The message OQQP was encrypted with a shift of 2. What is the original word?

    1. A) MOON
    2. B) CAKE
    3. C) LNNM
    4. D) TREE
    5. E) NPPO
    Show the solution
    Answer: A) MOON

    How it works: O→M, Q→O, Q→O, P→N

  3. Question 3 Hard

    The Caesar cipher moves every letter the same number of places on in the alphabet (after the last letter comes the first again). Alphabet: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z. The word MOON was encrypted as PRRQ. By how many places were the letters shifted?

    Show the solution
    Answer: 3

    How it works: M→P, O→R, O→R, N→Q

Related topics

All Computing topics

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