Two spies have to communicate using secret code. they need to create exactly 30 possible precoded messages, using a single number and letter. which structure should the code have? a. select a number from {1, 2, 3, 4} and a vowel
b. select a number from {1, 2, 3, 4, 5} and a vowel.

c. select a number from {1, 2, 3, 4, 5, 6} and a vowel.

d. select a number from {1, 2, 3, 4, 5} and a consonant

The code should have the structure C.

Step-by-step explanation:

Given : Two spies have to communicate using secret code. They need to create exactly 30 possible precoded messages, using a single number and letter.

To Find: Which structure should the code have?

Solution:

The structure that have 30 possible outcomes , the code should have that structure .

Option A:  Select a number from {1, 2, 3, 4} and a vowel

Since we are given that the code contains one number and one letter

No.of vowels = {a,e,i,o,u}=5

Out of these five we will choose only one

We are supposed to choose a number from {1, 2, 3, 4}

Out of these four numbers we will choose only one

Now to find no. of possible outcomes we will use combination

Formula :

So, no. of possible outcomes from option A  :

Thus no. of possible outcomes from Option A is 20.

Option B: Select a number from {1, 2, 3, 4, 5} and a vowel.

Since we are given that the code contains one number and one letter

No.of vowels = {a,e,i,o,u}=5

Out of these five we will choose only one

We are supposed to choose a number from {1, 2, 3, 4,5}

Out of these five numbers we will choose only one

So, no. of possible outcomes from option B  :

Thus no. of possible outcomes from Option B is 25.

Option C: Select a number from {1, 2, 3, 4, 5, 6} and a vowel.

Since we are given that the code contains one number and one letter

No.of vowels = {a,e,i,o,u}=5

Out of these five we will choose only one

We are supposed to choose a number from {1, 2, 3, 4,5,6}

Out of these six numbers we will choose only one

So, no. of possible outcomes from option C :

Thus no. of possible outcomes from Option C is 30.

So, Option C is correct

Option D:  Select a number from {1, 2, 3, 4, 5} and a consonant

Since we are given that the code contains one number and one letter

No.of consonants  = 21

Out of these twenty one we will choose only one

We are supposed to choose a number from {1, 2, 3, 4,5}

Out of these five numbers we will choose only one

So, no. of possible outcomes from option C :

Thus no. of possible outcomes from Option D is 105.

Hence Option C is correct because no. of possible outcomes in that case is 30 .

So, the code should have the structure C.