in an AP, the difference between the 8th term and the 4th term is 20, and the 8th term is 1.5 times the 4th term. What is the common difference?

Question

anonymous · Answer

Am I misssing something ... $ (a+7d) - (a+3d) = 20 \implies d = 5 $

hoblos · Answer

common difference=5
4th term is 40
8th term is 60

anonymous · Answer

missing*

anonymous · Answer

Aha I got the right answer! but why that redundant information?

sasogeek · Answer

what redundant information?

anonymous · Answer

"and the 8th term is 1.5 times the 4th term"

hoblos · Answer

i guessed he may need to calculate the 4th and 8th terms

sasogeek · Answer

well there's a second question which i didn't add,i just typed what was in the book but the question i didn't add was find the first term of the sequence, not sure how that helps though :|

anonymous · Answer

@hoblos: Hm,  that seems to be a valid assumption.

anonymous · Answer

saso, read about arithmetic progression.

sasogeek · Answer

i thought if i typed this out, i'd be able to figure out the first term myself so i didn't have to add it :P

sasogeek · Answer

i've studied series and sequence before, AP, GP, :P i'm only revising/studying what i've forgotten and thought i should ask this cos it was bugging me :P thanks for the help though :D

anonymous · Answer

$$ \stackrel{\circ.\circ}{\huge o}\angle\huge\lbrace\normalsize\text{Fair Enough! I'm sooo tired, take care saso } \large\ddot \smile  $$

sasogeek · Answer

you too :)