I can see that the pattern is that starting from 1, you add 3 to each number. But what’s the shortcut to figure out the 100th digit in the squence?

It’s the 100th term, not the 100th digit.

Also, you may want to revisit the videos on how the sum of intervals are computed.

I meant ‘term’ yea. Semantics.

Thanks for the kinda vague advice lol…can you give a clearer tip or point me in the right direction to find the videos you’re talking about?

Notice that the question is (literally) asking for the sum of an interval (in this case from 1 to 100 \times 3 + 1) divided by the number of elements, in this case 100. You can hence use the concepts in the “Sum of Multiples in Interval” video to solve the problem.

Alternatively, the question is hinting that the mean is equal to the median. We have 100 terms in the sequence; can you find the 50th and 51st terms of the sequence? Can you use this to find the median, and hence the mean, of the given sequence?