In the eight term sequence A, B, C, D, E, F, G, H, the value of C is 5

First I started from this; (A + B + C) + (C + D + E) + (F + G + H) =90 since A + B + C =30, C + D + E=30 and F + G + H=30

Then, if we rearrange that equation, A + ( B + C + D) + C + (E + F + G) + H =90

If we then do some math,

A + H = 90 - ( ( B + C + D) + C + (E + F + G) ) which is 25.

Therefore C

Since C = 5, if we let A = 10, then B must be 15 so that A + B + C = 30. Now D must be 10 so that B + C + D = 30 and E must be 15 so that C + D + E = 30. If we continue the process, we have:

A, B, C, D, E, F, G, and H as 10, 15, 5, 10, 15, 5, 10, and 15, respectively.

Therefore, A + H = 10 + 15 = 25.

(Note: We will leave to readers to try a different number for A and see that, regardless of the choice of the value of A, you will always have A + H = 25.)

Alternate Solution:

Since A + B + C = B + C + D; we have A + B + C - (B + C + D) = A + B + C - B - C - D = A - D = 0; therefore A = D. Applying the same argument, for example for B + C + D = C + D + E, we can conclude B = E and continue in the same way to obtain C = F, D = G and E = H. Since B = E = H, we have

A + B + C = 30

A + H + 5 = 30

A + H = 25

Answer: C

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.