Posted by **Speedo** on Saturday, September 7, 2013 at 3:02pm.

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.

- mAtH -
**Steve**, Saturday, September 7, 2013 at 4:11pm
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.

- mAtH -
**Speedo**, Saturday, September 7, 2013 at 4:33pm
This is what you did wrong, i think. YOu multiply not add.

- mAtH -
**Steve**, Saturday, September 7, 2013 at 4:47pm
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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