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(a) 15% of 250

(b) 1% of 1 hour

(c) 20% of Rs 2000.

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a.Step I: The given value is 250.

Step II: We consider the unknown value as x

Step III: we will take 250 as 100% hence we get, $ 250 = 100\% $ .

Step IV: in the same way, the unknown value x is 15% then we get, x = 15% .

Step V: so we have two equations,

250 = 100% ………………….(i)

x = 15% ………………………(ii)

Step IV: dividing the equation (i) by the equation (ii) then we get,

$

\dfrac{{250}}{x} = \dfrac{{100\% }}{{15\% }}\\

\dfrac{{250}}{x} = \dfrac{{100}}{{15}}\\

250 \times 15 = 100 \times x

$

On simplifying the equation we get,

$

x = \dfrac{{250 \times 15}}{{100}}\\

x = \dfrac{{3750}}{{100}}\\

x = 37.5

$

Hence the $ 15\% $ of 250 is 37.5

b.Step I: The given value is 1 hour.

Step II: We consider the unknown value as x

Step III: we will take 1 hour as $ 100\% $ hence we get, $ 1\;{\rm{hour}} = 60\;{\rm{minutes = }}100\% $ .

Step IV: In the same way, the unknown value x is $ 1\% $ then we get, $ x = 1\% $ .

Step V: so we have two equations,

$ 60\;{\rm{minutes}} = 100\% $ ………………….(i)

$ x = 1\% $ ………………………(ii)

Step IV: dividing the equation (i) by the equation (ii) then we get,

$

\dfrac{{60\;{\rm{minutes}}}}{x} = \dfrac{{100\% }}{{1\% }}\\

\dfrac{{60\;{\rm{minutes}}}}{x} = \dfrac{{100}}{1}\\

60\;{\rm{minutes}} \times 1 = 100 \times x

$

On simplifying the equation we get,

$

x = \dfrac{{60\;{\rm{minutes}} \times 1}}{{100}}\\

x = \dfrac{{60\;{\rm{minutes}}}}{{100}}\\

x = 0.6\;{\rm{minutes}}

$

Hence the $ 1\% $ of 1 hour is $ 0.6\;{\rm{minutes}} $ .

c.Step I: The given value is Rs 2000.

Step II: We consider the unknown value as x

Step III: we will take Rs 2000 as $ 100\% $ hence we get, $ {\rm{Rs }}2000 = 100\% $ .

Step IV: In the same way, the unknown value x is $ 20\% $ then we get, $ x = 20\% $ .

Step V: so we have two equations,

$ {\rm{Rs }}2000 = 100\% $ ………………….(i)

$ x = 20\% $ ………………………(ii)

Step IV: dividing the equation (i) by the equation (ii) then we get,

$

\dfrac{{{\rm{Rs }}2000}}{x} = \dfrac{{100\% }}{{20\% }}\\

\dfrac{{{\rm{Rs }}2000}}{x} = \dfrac{{100}}{{20}}\\

{\rm{Rs }}2000 \times 20 = 100 \times x

$

On simplifying the equation we get,

$

x = \dfrac{{{\rm{Rs }}2000 \times 20}}{{100}}\\

x = \dfrac{{40000}}{{100}}\\

x = 400

$

Hence the $ 20\% $ of Rs 2000 is 400