Moderate -0.3 This is a straightforward geometric progression question requiring standard formulas. Students need to find the common ratio from two given terms (r² = 2/18), then the first term, and finally apply the sum to infinity formula. While it involves multiple steps, each is routine application of GP formulas with no conceptual challenges beyond C2 level expectations.
The second term of a geometric progression is 18 and the fourth term is 2. The common ratio is positive. Find the sum to infinity of this progression. [5]
Question 8:
8 | r = 1/3 s.o.i.
a = 54 or ft 18 ÷ their r
a
S = used with -1 < r < 1
1−r
S = 81 c.a.o. | 2
M1
M1
A1 | 1 mark for ar = 18 and ar3 = 2 s.o.i. | 5
The second term of a geometric progression is 18 and the fourth term is 2. The common ratio is positive. Find the sum to infinity of this progression. [5]
\hfill \mbox{\textit{OCR MEI C2 Q8 [5]}}