Common rule – Master IBM IPAT

In common rule series, as the name suggests, all numbers follow a common mathematical rule.

Here is an example –

Q) 2 4 8 16 20 ?

a] 40

b] 43

c] 45

d] 47

Solution

The solution is a] 40 as all the numbers in the given series are even.

Readers may question – Just when do we actually use the common rule technique to find the solution given there may be many ways to decipher the series. The general rule is that when other techniques such as difference patterns don’t work out, that’s a great time to think about common rules binding the numbers together. Thus, the common rule method is a actually secondary method but is something that serious Ipat test takers must be aware of.

The following are a few practice examples. Please do attempt to solve the questions before reading the solutions.

Q) 2 3 5 7 11 13 ?

Solution

Solution – 17. Notice the series corresponds to consecutive prime numbers with 17 being the next prime number

Q) 5 10 17 26 ?

Solution

Solution – 37. Notice the series is related to the square of number as follows

5 = 2²+1

10 = 3²+1

17 = 4²+1

26 = 5²+1

Hence the next number is 37 = 6²+1

Q) 343 119 49 70 ?

a] 111

b] 62

c] 52

d] 763

Solution

Solution – d] 763. Immediately notice that all the numbers are divisible by 7.

Q) 3 11 85 1029 ?

Solution

Solution – 15631. Notice the series is of the form

3 = 1²+2

11 = 2³+3

85 = 3⁴+4

1029 = 4⁵+5

Hence, the next number is 15631 (5⁶+6)

Excellent job if you got the last question right!

The real secret of cracking the IPAT is practicing enough relevant questions so that you can easily relate back such patterns in the test. Trust us, practice does help immensely, especially in the timed situation of the real test. We have developed a comprehensive numeric series question practice book specifically catering to the IPAT format which you can find here and we guarantee you will find it very useful in preparing for the test.

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