Which term of the G.P. 5, 10, 20, 40, … is 5120 ?
Question
Which term of the G.P. 5, 10, 20, 40, … is 5120 ?
Solution
The given sequence is a geometric progression (G.P.) where each term is multiplied by a common ratio to get the next term.
The general formula for the nth term of a G.P. is given by a*r^(n-1), where:
- a is the first term of the sequence,
- r is the common ratio, and
- n is the term number.
In this case, a = 5 (the first term), r = 2 (each term is twice the previous term), and we want to find n such that the nth term is 5120.
So, we set up the equation 5*2^(n-1) = 5120 and solve for n:
- Divide both sides by 5: 2^(n-1) = 1024
- Recognize that 1024 is a power of 2: 1024 = 2^10, so 2^(n-1) = 2^10
- Since the bases are equal, the exponents must be equal: n-1 = 10
- Solve for n: n = 10 + 1 = 11
So, the 11th term of the geometric progression is 5120.
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