Answer:
Step-by-step explanation:
Here, we want to show that the sum is divided by 15
From what we have, the given sum is a geometric sequence
The first term is 1
Now, the pattern of ending afterwards will be 2, 4, 6 and 8
This ending keeps repeating itself
This 2,4,6,8 pattern could repeat itself 24 times
So we have a total of 1 + 24(4) = 97 terms
To make it 100, we have the last three terms as 2,4 and 8
So we have the ending number ONLY sum as follows:
1 + 24(2+4+6+8) + 2 + 4 + 8 = 1 + 480 + 14 = 495
We can divide this by 15 and that gives 495/15 = 33
That shows that the sum is divisible by 15
Secondly, we want to show that S has at least 30 digits
We can infer this from the last terms
We can write 2^99 as 2^33 * 2^33 * 2^33
A single 2^33 has a value of 8,589,934,592
That means 10 digits
The other two has 10 digits too
The sum of all possible digits in the largest term is 10 + 10 + 10 = 30
That makes a total of 30
The question states 30 or more
Hence, this is correct