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Tamil Nadu Board of Secondary EducationSSLC (English Medium) Class 8

Find the rate of compound interest at which a principal becomes 1.69 times itself in 2 years

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Question

Find the rate of compound interest at which a principal becomes 1.69 times itself in 2 years

Sum
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Solution

Let principal be ‘P’

Amount is given to be 1.69 times principal

i.e 1.69 P

Time period is 2 years. = (n)

Rate of interest = r = ? ...(required)

Applying the formula,

Amount = `"Principal" (1 + "r"/100)^"n"`

Substituting 1.69 P = `"P"(1 + "r"/100)^2`

∴ `(1 + "r"/100)^2 = (1.69"P")/"P"` = 1.69

Taking square root on both sides, we get

`sqrt(1.69) = 1 + "r"/100`

∴ `1 + "r"/100` = 1.3

∴ `"r"/100` = 1.3

r = 30%

∴ rate of compound interest is 30%

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Chapter 4: Life Mathematics - Exercise 4.5 [Page 152]

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Samacheer Kalvi Mathematics [English] Class 8 TN Board
Chapter 4 Life Mathematics
Exercise 4.5 | Q 12 | Page 152
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