Skip to content
MathsGenie logo
Quick links
Open app

Course home

  1. A Level
  3. Maths OCR (MEI)
  5. Question bank

1.6.15 Standard formulae for geometric series (A-level only)

Medium
123456789101112131415161718192021222324252627
Question 15

A company’s net cash flow in year nnn, denoted by PnP_nPn​ (in millions of dollars), follows a geometric progression with common ratio rrr.

You are given that:

  • The sum of the cash flows in the second and third years is P2+P3=10P_2 + P_3 = 10P2​+P3​=10
  • The cash flow in the fourth year is P4=20P_4 = 20P4​=20
a.

Show that r r\,r satisfies the equation r2−2r−2=0r^2 - 2r - 2 = 0r2−2r−2=0.

[4]
b.

Given that the sum of the cash flows over an infinite time period, ∑n=1∞Pn\sum_{n=1}^{\infty} P_n∑n=1∞​Pn​, is convergent,

find the exact value of P1P_1P1​.

[4]
c.

Hence, calculate the exact value of S∞S_\inftyS∞​.

[3]

1.6.15 Standard formulae for geometric series (A-level only) Questions

  1. A Level
  2. /Maths
  3. /1.6.15 Standard formulae for geometric series (A-level only)