Fill in the missing number

155?

175?

Would you please show how your answer was determined?

Would you please show how your answer was determined?

The first thing that I noticed was that all of the digits are odd and that within each number the digits are in numerical order.

The second thing I noticed is that the third and fifth numbers contain only the digits 3 and 5, and that the fifth number is the same as the third with the addition of a 5.

So one interpretation is that this is a nested double sequence with the first two numbers acting as seed values (the first number for the first sequence, and the second number for the second sequence). The second term of the first sequence adds a prefix digit, while the second term of the second sequence adds a suffix digit. Therefore each sequence alternates between prefix and suffix digits with each term, while always being opposite to one another in that respect.

The fourth number could be 115 (being the second term of the second sequence it adds a suffix digit). The series could continue:

5, 15, 35, 155, 355, 1155, 3355, 11555...

This is a weakly inferred pattern but seems logically consistent.

I find that numerical pattern puzzles can be amenable to more than one solution. It could also be the case that your sequence is not a puzzle at all but simply random.

no.

The series is:

5 , 15 , 35 , 75 , 355

The answer is 75

5 (No symbol) divided by 5 = 1
Place 1 b4 5 = 15
15 (No symbol) divided by 5 = 3
Place 3 b4 5 = 35
35 (No symbol) divided by 5 = 7
Place 7 b4 5 = 75
75 (No symbol) divided by 5 = 15
Place 15 b4 5 = 155
155 (No symbol) divided by 5 = 31
Place 31 b4 5 = 315.

I think you posted the wrong numbers, scribbler. Mine are better.

It's not a geometric progression.

There is no typographical or logical error in the question or the answer.

I agree.
But I got the '75', did I not?

Without the 'key' a door cannot be opened easily.

Try this: Which number is missing?

10 .. 12 14 ?