Question

1 3 21 71 ___ 331 find the missing no.?

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Answer 1

answer 1 3 2171 4 331 answers

Answer 2

Concept:

This question requires us to have knowledge on how to solve mental ability questions and some basic usage of arithmetic operations.

Given:

We are given a sequence of numbers 1, 3, 21, 71, __, 331.

To find:

We need to find the given missing number.

Solution:

Let the missing number be x.

Let us first subtract the 2nd number with the 1st and so on.

3-1 = 2

21-3 = 18

71-21= 50

x- 71= y

Now we subtract the 2nd subtracted number with the first subtracted number and 3rd with 2nd.

18-2 = 16

50-18 = 32

y-50=48

Now, we can observe that these numbers are a multiple of 16.

The next multiple of 16 would be 48.

therefore the next difference in the sequence will be

48+50=y = 98.

Therefore,

x = 98+71 = 169

Also, we can notice that the next number follows the same rule.

The missing number is 169.