High School

Find the sum of the first 6 terms of the following sequence. Round to the nearest hundredth if necessary.

7, -21, 63, ...

A. -220
B. -218.73
C. 218.73
D. 220

Answer :

The sum of the first 6 terms of the geometric sequence is found by adding the terms together, resulting in -2274. Rounding this to the nearest hundredth as instructed gives us -220. Hence the correct option is (b).

The sequence in question is a geometric sequence where each term is obtained by multiplying the previous term by -3 (since 7 / -3 = -21, and -21 imes -3 = 63, etc.).

To find the sum of the first 6 terms, we first identify the next terms in the sequence: 7, -21, 63, -189, 567, -1701.

The sum of these terms is the total when we add them together: S = 7 + (-21) + 63 + (-189) + 567 + (-1701) = -2274.

Since there are no decimal places in the sequence, no rounding to the nearest hundredth is necessary.

Thus, the correct answer is b) -220 because -2274 rounded to the nearest hundredth is -220.

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