Study the sequence/pattern of letters or numbers carefully to work out the pattern on which it is based, and answer what the next item in the sequence must be.

For example, the sequence ‘A,C,E,G,?’ has odd numbered letters of alphabet, therefore, the next item must be ‘I’.

0, 3, 8, 15 ?

The correct answer is 24.

Let's analyze the given numerical sequence step-by-step to determine the underlying pattern:

Method 1: Observing the difference between consecutive terms

Let's find the difference between each term and the next term in the sequence:

$3-0=3$

$8-3=5$

$15-8=7$

Notice that the differences between consecutive terms are consecutive odd numbers: 3, 5, 7. Following this pattern, the next difference must be 9.

Adding 9 to the last term (15) gives:

$15+9=24$

Method 2: Using perfect squares minus one

Alternatively, we can express each term as $n^2-1$ where $n$ starts from 1:

First term (n = 1): $1^2-1=1-1=0$

Second term (n = 2): $2^2-1=4-1=3$

Third term (n = 3): $3^2-1=9-1=8$

Fourth term (n = 4): $4^2-1=16-1=15$

Following this rule, the fifth term (n = 5) is:

$5^2-1=25-1=24$

Both methods consistently lead to 24 as the next number in the sequence.