CHALLENGE

GRADE  4 - 6 / Age 9-11

Coding and Decoding...

You can make secret codes by letting numbers represent letters of the alphabet.  For instance, we can assign the following values:

Vowels:  A=6, E=8, I=4, O=2, U=10, *=0(zero)

Consonants:  B=1, C=3, D=5, F=7, G=9, H=11, J=13, K=15, L=17, M=19, N=21, P=23, Q=25, R=27, S=29, T=31, V=33, W=35, X=37, Y=39, Z=41.

CODING

So, to code the word "CAT,"  we find the numbers for each letter.  Look up C and you'll find that C=3.  Look up A and you'll find that A=6. Finally, look up T and you'll find T=31.  So, "CAT" is   3-6-31.

DECODING

Now, let's decode a word and see what we get.  Decode 5-2-9.  

What is 5?  5=D.  What is 2?  2=O.  What is 9?  9=G.

So, 5-2-9 is DOG!

EXERCISE I

A)  Code each word below.

SPOON

MATH

COMPUTER

B)  Decode each word below.

23-8-21

8-27-6-29-8-27

29-8-3-27-8-31

C)  Code the name of your school or last name.

As you can see, if you know how to decode, coding can be a great way to send secret messages.  Now, notice there are two kinds of letters, vowels (a,e,i,o,u) and consonants (all the rest).  Notice that the vowels are coded with even numbers and the consonants are coded with odd numbers.  So, vowels=even and consonants=odd.  We can make our code better.  Let's make:

vowels=even-2

and

consonants=odd+2.

Now, to code "CAT,"  C is a consonant, so C=3+2=5, A is a vowel so A=6-2=4, and T is a consonant so T=31+2=33.  So, "CAT" is 5-4-33.

Now, decoding requires you to remove the code and can be even trickier!

Exercise II

A)  Code the messages below using our new code.

MATH IS FUN.

I LOVE TO LEARN.

COMPUTERS ARE COOL.

B)  Decode the messages below using our new code.

3-4-23-4-23-4

41-0-8-7-2-7-2-33

5-4-19-19-33-13-6-23-0-19-2-5-6

Finally, we can really soup up our code by coding our message with our formulas and then changing to the letters that come out.  So, "CAT" becomes C=3+2=5=D, A=6-2=4=I, T=31+2=33=V.   So, "CAT" is now "DIV" in our new code.

A)  Code these messages into a new word message.

CODE WORD

ELEPHANTS NEVER FORGET.

ZEBRAS ARE IN THE ZOO (Note:  Can this be done?  If not, what can be done so that the code will work?)

B)  Decode this message into a readable messages.

NATTIHA NAAV NA

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