Deciphering Affine Cipher Messages with Reciprocals

Miss Bunton introduces a lesson on using reciprocals and mods to solve congruences and decipher messages in affine ciphers. The lesson includes listing reciprocal pairs in mod 26, solving congruences using these reciprocals, and applying the method to decipher messages. Students are encouraged to work on provided worksheets and check their answers with an answer key. The video concludes with instructions for an assignment and information on office hours for additional support.

What is the main topic of Miss Bunton's lesson?

• Learning about geometric shapes

• Using reciprocals and mods to solve equations and decipher messages

• Solving quadratic equations

• Understanding linear algebra

Tags

CCSS.RI.6.4

CCSS.RI.7.4

CCSS.RI.8.4

CCSS.RI.9-10.4

CCSS.RI.9-10.4

Which mod is used for finding reciprocals in the review section?

• Mod 10

• Mod 20

• Mod 15

• Mod 26

Which pair of numbers are reciprocals in mod 26?

• 2 and 13

• 3 and 9

• 4 and 22

• 6 and 18

What is the first step in solving the congruence 19X ≡ 7 (mod 26)?

• Adding 5

• Multiplying by 19

• Subtracting 5

• Dividing by 7

What is the reciprocal of 19 in mod 26?

• 11

• 15

• 25

• 21

Tags

CCSS.7.EE.B.3

What is the final value of X in the congruence 19X ≡ 7 (mod 26)?

• 26

• 25

• 24

• 23

In the deciphering example, what is the reciprocal of 7 in mod 26?

• 11

• 19

• 15

• 23

Tags

CCSS.HSA.APR.D.6

What is the plaintext letter corresponding to the cipher text letter 'Z' in the example?

• U

• T

• S

• R

What is the final deciphered word in the example?

• STUDY

• WRITE

• LEARN

• TEACH

Tags

CCSS.L.3.2F

What is the first step in finding the reciprocal of 7 in mod 11?

• Adding 11 until divisible

• Multiplying by 11

• Subtracting 7

• Adding 7