Calculate the sum and mean of a numerical sequence

Question

In sequence 3,5,7,9,11,13,15. Discover the pattern of the sequence and:

• a) Make a program to display 12 values of this sequence started by 3.
• b) Show the sum of 'ALL' values (12 values).
• c) Show the mean value of 'ALL' values (12 values).

I started out like this, so I curled up. Help me.

x = 3
while x < 27:
   print(x)
   x = x + 2

Answer 1

Note: it is important to note that there are infinite number series that satisfy the sequence {3,5,7,9,11,13,15,...} (view end of reply), then ask the user to identify the standard makes no sense and especially if any of the series were implemented, it would be a valid solution. The solution a_n = 2*n + 1 is possibly the most trivial of them and, probably for that reason, will be the one expected by the teacher.

You have already done the letter (a), but there is a way to improve. The way you did, you need to initially know that to display the 12 requested elements the condition will be x < 27, But what if you’re asked for 20, 50 or even don’t even know how many? Then your solution wouldn’t work. The simplest is to create a counter that controls how many numbers will be displayed:

quantidade = 12
exibidos = 0
numero = 3

while exibidos < quantidade:
    print(numero)
    numero += 2
    exibidos += 1

Thus, the 12 numbers in the sequence will be shown. If you change quantidade to 50, will show the 50. Already, for the letter (b), you need to accumulate the sum in another variable:

quantidade = 12
exibidos = 0
numero = 3
soma = 0

while exibidos < quantidade:
    print(numero)
    soma += numero
    numero += 2
    exibidos += 1

print('Soma = ', soma)

And finally, the average will be the division between the sum and the amount of numbers:

media = soma / quantidade

Staying:

quantidade = 12
exibidos = 0
numero = 3
soma = 0

while exibidos < quantidade:
    print(numero)
    soma += numero
    numero += 2
    exibidos += 1

print('Soma = ', soma)

media = soma / quantidade

print('Média = ', media)

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Collaboration of Jefferson Quesado

As we are dealing with numerical sequences, the continuity of the generating function is not a requirement, so, for example, the sequence generated by:

It satisfies the sequence given in the statement, but the following term would be 21 (not 17). The sequence would be: 3, 5, 7, 9, 11, 13, 15, 21, 23, 25, ...

Collaboration of Bacchus

Another much simpler to understand is the sequence given by:

That is, calculate the rest of the 2x+1 division by 17, so the generated sequence would be: 3, 5, 7, 9, 11, 13, 15, 0, 2, 4, 6, ..., which also satisfies the sequence given in the statement, but the following term is not 17.

Answer 2

Sequence to be shown: 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25.

In place of while x < 27 place x <= 25 and also create an auxiliary variable to store the sum of values.

Example: y = 0 (start it with 0 so there is no dirt left over from the sums and give wrong values).

I don’t know how to do it in Phyton, I made an example using Java logic.

x = 3;
y = 0;

   while x < 27:
       print(x)
         y = x + 2;
         x++;

Answer 3

Follows the solution:

# Geracao da sequencia contendo 12 valores
seq = list(range(3, 27, 2))

# Extrai valores da sequencia iniciados com '3'
a = [ n for n in seq if str(n)[0] == '3' ]

# Calcula soma dos valores da sequencia
b = sum(seq)

# Calcula a media dos valores da sequencia 
c = sum(seq) / float(len(seq))

print(seq)
print(a)
print(b)
print(c)

Exit:

[3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25]
[3]
168
14.0