Two spies have to communicate using a 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.

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

Step-by-step explanation:

Let's start this with a simple example: how many messages are possible using one number from {7, 9} and one letter from {a, b}. It will be 4 as 7a, 7b, 9a and  9b. This result can also come by multiplying the number of digits used and number of alphabets used - here number of digits are 2 (they are 7 and 9) and number of alphabets used are 2 (they are 'a' and 'b'). So 2 × 2 = 4.

[NOTE : In this question 7a and a7 are same]

Maximum number of options consists of vowels as letters so we will first find the number of digits needed if vowels are used as letters.

The number of vowels are 5 (they are 'a', 'e', 'i', 'o', 'u').

The number of possible precodes needed = 30

Let the number of digits needed be 'n'.

Then n × 5 = 30

∴ n = 6

Therefore the number of digits needed is 6 which is there in option C. The digits are {1, 2, 3, 4, 5, 6}

Therefore option C is the answer.

step-by-step explanation:

ok one would be money, and the other would be refreshments or something similar. if each bag of popcorn is 5.00 and each drink is half of that that means drinks are 2.50 the proper way to do that would to look and see how much of each you can buy without exceeding a limit of 30.00

let's cover over the formula of the vertex:

y = a(x – h)^2 + k

in this formula, (h,k) are the vertex, always remember that the positive or negative value of the vertex is based on the sign it has.

for example, if the vertex is -3,-6 then both the x and y value would have the positive sign attached to it and if it were a positive x and y value, then a negative sign would be attached to it.

with that being said, for our problem the x value is a positive one so we are looking for a number with a negative sign next to it, in this case the first and second choice.

however, for the first answer choice it isn't quite part of the formula so we know that the answer choice correctly displays the x value.

to confirm, we can see if the -1 fits correctly with the second answer choice, and as mentioned above a negative number will have a positive sign attached to it. so, for our problem we can see that -1 has been changed to +1, so we can confirm that the second answer choice is correct.

hence, our final answer is y=(x - 1)^2 + 1