If the pattern below follows the rule "add 6 to the previous number and then multiply the result by 3" what is the third number in the pattern, based on the initial number 1?

1, __, Δ, .....

1

(6+1)3 = 21
(6+21)3 = 81 etc....

To find the third number in the pattern, we first need to follow the given rule. The rule states that we need to add 6 to the previous number and then multiply the result by 3.

Starting with the initial number, which is 1, we can apply the rule step by step:

Step 1: Add 6 to the previous number (1 + 6 = 7)
Step 2: Multiply the result by 3 ((7) * 3 = 21)

Therefore, the third number in the pattern is 21.