Final answer:
The missing number in the sequence 1, 3, 9, 27, 81 is 243.
Step-by-step explanation:
The missing number in the sequence 1, 3, 9, 27, 81 is 243.
Each number in the sequence is obtained by multiplying the previous number by 3. For example, 3 x 1 = 3, 3 x 3 = 9, 3 x 9 = 27, and so on. Therefore, to find the missing number, we multiply 81 by 3, resulting in 243.