Answer: 26, 31, and 36
Step-by-step explanation: To find the next three terms in the pattern 1, 6, 11, 16, 21 and so on, notice that we add 5 to get from 1 to 6. Next we add 5 to get from 6 to 11. Next we add 5 to get from 11 to 16 and we finally add 5 to get from 16 to 21.
Continuing with the same pattern, we would then add 5 to 21 and we would get 26. Next we would add 5 to 26 and we would get 31. Finally we will add 5 to 31 and we will get 36.
Therefore, the next three terms in the sequence are 26, 31, and 36.