Asked by Speedo

The 23rd term in a certain geometric sequence is 16 and the 28th term in the sequence is 24. What is the 43rd term?

It is not 48.
Answered by Steve
a+22d = 16
a+27d = 24

a = -96/5
d = 8/5

-96/5 + 42*8/5 = -96/5 + 336/5 = 240/5 = 48

If 48 is marked wrong, the key is in error. You could have checked it yourself.
Answered by Speedo
This is what you did wrong, i think. YOu multiply not add.
Answered by Steve
Or, look at it this way. From T23 to T28 is 5 terms, and the value grew by 8.
From T28 to T43 is 15 terms = 3*5, so the value will grow by 3*8, or 24.

24+24 = 48
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