Problem
In a fund raising show, a group of philanthropists agreed that the first one to arrive would pay 25¢ to enter, and each later would pay twice as much as the preceding person. The total amount collected from all of them was \$262,143.75. How many of them paid?
Progression
Problem
How many terms from the progression 3, 5, 7, 9, ... must be taken in order that their sum will be 2600?
| A. 80 | C. 50 |
| B. 60 | D. 70 |
Derivation of Sum of Finite and Infinite Geometric Progression
Geometric Progression, GP
Geometric progression (also known as geometric sequence) is a sequence of numbers where the ratio of any two adjacent terms is constant. The constant ratio is called the common ratio, r of geometric progression. Each term therefore in geometric progression is found by multiplying the previous one by r.
Eaxamples of GP:
- 3, 6, 12, 24, … is a geometric progression with r = 2
- 10, -5, 2.5, -1.25, … is a geometric progression with r = -1/2
Derivation of Sum of Arithmetic Progression
Arithmetic Progression, AP
Definition
Examples of arithmetic progression are:
- 2, 5, 8, 11,... common difference = 3
- 23, 19, 15, 11,... common difference = -4
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