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Question
The population of a town decreased by 12% during 1998 and then increased by 8% during 1999. Find the population of the town, at the beginning of 1998, if at the end of 1999 its population was 2,85,120.
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Solution
Let the population in the beginning of 1998 = P
The population at the end of 1999 = 2,85,120(A)
r1 = - 12% and r2 = + 8%
∴ A = P`( 1 - r_1/100 )( 1 + r_2/100 )`
⇒ 2,85,120 = P`( 1 - 12/100 )( 1 + 8/100 )`
⇒ 2,85,120 = P`( 22/25 )( 27/25 )`
⇒ P = `[ 2,85,120 xx 25 xx 25 ]/[ 22 xx 27 ]` = 3,00,000.
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