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The value of an item depreciates x%x\% per year. The present value of the item is ₹109350₹ 109350. Its value after 3 years will be ₹79716.15₹ 79716.15. Two years ago from now, its value, in rupees, was

Solution

✅ Correct Option: 4

The value of an item depreciates x%x\% per year. The present value is ₹109350₹ 109350, and after 3 years it will be ₹79716.15₹ 79716.15.

Using the depreciation formula:

A=P(1−x100)nA = P\left(1 - \frac{x}{100}\right)^n

where AA is the final value, PP is the initial value, xx is the rate of depreciation, and nn is the time in years.


79716.15=109350(1−x100)379716.15 = 109350 \left(1 - \frac{x}{100}\right)^3

(1−x100)3=79716.15109350\left(1 - \frac{x}{100}\right)^3 = \frac{79716.15}{109350}

(1−x100)3=797161510935000\left(1 - \frac{x}{100}\right)^3 = \frac{7971615}{10935000}

(1−x100)3=7291000\left(1 - \frac{x}{100}\right)^3 = \frac{729}{1000}


Taking the cube root:

1−x100=729100031 - \frac{x}{100} = \sqrt[3]{\frac{729}{1000}}

1−x100=9101 - \frac{x}{100} = \frac{9}{10}

1−x100=0.91 - \frac{x}{100} = 0.9


Let the value of the item 2 years ago be VV. The present value is the result of depreciating VV for 2 years:

109350=V(0.9)2109350 = V (0.9)^2

109350=V(0.81)109350 = V (0.81)

V=1093500.81V = \frac{109350}{0.81}

V=1093500081V = \frac{10935000}{81}

V=135000V = 135000

The value of the item 2 years ago was ₹135000₹ 135000.

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