中等MATH-EXPL-007
What is the sum to infinity of 12 + 6 + 3 + …?
A. 18
B. 36
C. 6
D. 24✓ 答案
解說
The common ratio is 1/2, and |r| < 1, so S = a/(1 − r) = 12/(1/2) = 24. The value 36 uses the reciprocal of the ratio in the wrong place.
The common ratio is 1/2, and |r| < 1, so S = a/(1 − r) = 12/(1/2) = 24. The value 36 uses the reciprocal of the ratio in the wrong place.