## anonymous one year ago What is the value of a fourth term in a geometric sequence for which a1=10 and r=.5

1. SolomonZelman

$$\LARGE a_n=a_1\times {\rm r}^{\rm n -1}$$

2. SolomonZelman

this is for any geometric sequence.

3. SolomonZelman

Now, for the fourth term of any geometric sequence it will read: $$\LARGE a_4=a_1\times {\rm r}^{\rm 4 -1}$$ $$\LARGE a_4=a_1\times {\rm r}^{3}$$

4. SolomonZelman

knowing your a1=10, and r=5, plug that into: $$\LARGE a_4=a_1\times {\rm r}^{3}$$ and then calculate the $$a_4$$.

5. anonymous

So the answer would be 1250?

6. SolomonZelman

lets see $$a_4=10\times 5^3$$ $$a_4=10\times 125$$ $$a_4=1250$$ yes, your answer is correct:)

7. anonymous

The answer was 1.25...