# Misc 31 - Chapter 9 Class 11 Sequences and Series

Last updated at Jan. 11, 2019 by Teachoo

Last updated at Jan. 11, 2019 by Teachoo

Transcript

Misc 31 (Method 1) A manufacturer reckons that the value of a machine, which costs him Rs 15625, will depreciate each year by 20%. Find the estimated value at the end of 5 years. We use the formula A = P ("1 โ" ๐/100)^๐ Here, P = principal r = rate of depreciation n = number of years A be the depreciated value Putting values Depreciated value = 15625("1 " โ20/100)^5 = 15625("1 " โ1/5)^5 = 15625("1 " โ1/5)^5 = 15625 (4/5)^5 = (15625 ร 1024)/3125 = 5 ร 1025 = 5125 Thus, the depreciated value of the machine after 5 years is Rs. 5125 Misc 31 (Method 2) A manufacturer reckons that the value of a machine, which costs him Rs 15625, will depreciate each year by 20%. Find the estimated value at the end of 5 years. The series is 12500 , 10000, 8000,โฆ.. This is a G.P. as 10000/12500 = 0.8 & 8000/10000 = 0.8 So, common ratio = 0.8 & first term = a = 12500 We need to calculate amount at the end of 5th year i.e. a5 We know that nth term of GP is an = arn โ 1 Putting a = 12500, r = 0.8, n = 5 a5 = 12500(0.8)5 โ 1 = 12500(0.8)4 = Rs. 5120 Hence value of machine after 5 years is Rs. 5120

Miscellaneous

Misc 1

Misc 2

Misc 3 Important

Misc 4

Misc 5

Misc 6

Misc 7 Important

Misc 8

Misc 9

Misc 10

Misc 11

Misc 12

Misc 13

Misc 14

Misc 15

Misc 16 Important

Misc 17

Misc 18

Misc 19 Important

Misc 20

Misc 21

Misc 22

Misc 23

Misc 24

Misc 25 Important

Misc 26

Misc 27

Misc 28 Important

Misc 29

Misc 30

Misc 31 You are here

Misc 32 Important

About the Author

Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 10 years. He provides courses for Maths and Science at Teachoo.