18:162::36:?

Use ratio / cross multiplication

18:162 ≡ 36:x

x=162*36/18
= 324

To find the missing number in the sequence 18:162::36:?, we need to understand the pattern or relationship between the given numbers.

The numbers in the sequence are divided by colons (::), indicating a certain pattern or rule. Looking at the given sequence, we can see that the first number, 18, is related to the second number, 162, in some way. Similarly, the third number, 36, should have a similar relationship with the missing number.

One common way of establishing a relationship between numbers in a sequence is by multiplication or division. Let's analyze the given sequence using these operations:

18 * 9 = 162 (multiplied by 9)
36 * 9 = 324 (multiplied by 9)

From this analysis, it becomes evident that each number is multiplied by 9 to get the next number in the sequence. Therefore, to find the missing number, we need to multiply 36 by 9.

36 * 9 = 324

Therefore, the missing number in the sequence 18:162::36:? is 324.