Stoopid sequences and series (1 Viewer)

[Sammmmmuel]

I can do every question in the sequences and series (Jones and Couchman) book, but this one i cant get the same answer as in the back. If any one else can be bothered to do this question and get the right answer it would be much appreciated:
Find the sum of all the positive integers less than 100, which are not divisible by six?
I think the answer is 4150 but the back of the book says 4134??

 

[Huy]

Are you sure that it's not 4234?

Sum of the first number of terms, which are divisible by 6, between 1-100:

S(16) = 16/2 [6+96]
= 8 x 104
= 816

Sum of the first 100 terms:

S(100) = 100/2 [1+101]
= 50 x 101
= 5050

5050 - 816
= 4234

 

[Sammmmmuel]

*feels embarressed* i knew dat!
Shit the simplest ones always seem harder to me than the "more difficult questions". Thanks Huy

 

[Huy]

No problem