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Example 16 - Chapter 9 Class 11 Sequences and Series (Term 1)
Last updated at March 30, 2023 by Teachoo
Examples
Example 1 (i)
Example 1 (ii)
Example 2
Example 3 Important
Example 4 Deleted for CBSE Board 2023 Exams
Example 5 Deleted for CBSE Board 2023 Exams
Example 6 Important Deleted for CBSE Board 2023 Exams
Example 7 Deleted for CBSE Board 2023 Exams
Example 8 Important
Example 9
Example 10 Important
Example 11
Example 12 Important
Example 13
Example 14 Important
Example 15 Important
Example 16 You are here
Example 17 Important
Example 18 Important
Example 19 Important Deleted for CBSE Board 2023 Exams
Example 20 Deleted for CBSE Board 2023 Exams
Example 21 Important
Example 22
Example 23
Example 24 Important
Chapter 9 Class 11 Sequences and Series
Serial order wise
- Ex 9.1
- Ex 9.2
- Ex 9.3
- Ex 9.4
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Examples
- Miscellaneous
Transcript
Example 16, A person has 2 parents, 4 grandparents, 8 great grandparents, and so on. Find the number of his ancestors during the ten generations preceding his own. The number of ancestors are 2,4,8,16, … It is a G.P. since, 4/2 = 2 8/4 = 2 ∴ Common ratio = 2 First term = a = 2 & number of generations (n) = 10 We have to find the number of his ancestors during the ten generations preceding his own, i.e. S10 As r > 1 Sum of n terms in GP = (a(𝑟^𝑛 − 1))/(r − 1) i.e. Sn = (a(𝑟^𝑛 − 1))/(r − 1) Putting values of a=2, r=2, & n=10 S10 = (2(210 − 1))/(2 − 1) S10 = (2(210 − 1))/1 S10 = (210 + 1 – 2) S10 = 211 – 2 S10 = 2048 – 2 S10 = 2046 Hence, the number of ancestors preceding the person is 2046.
