Calvin Learnt Percentages!

By converting the percentage into fractions, we have $10\% = \dfrac{10}{100}, 20\% = \dfrac{20}{100}, 30\% = \dfrac{30}{100}, 40\% = \dfrac{40}{100} .$

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Thus, $10\%$ of $20\%$ of $30\%$ of $40\%$ of $25000$ is equals to

$\begin{aligned} &&\dfrac{10}{100} \times \dfrac{20}{100} \times \dfrac{30}{100} \times\dfrac{40}{100} \times 25000 \\ &=& \dfrac{1\cancel0}{10\cancel0} \times \dfrac{2\cancel0}{10\cancel0} \times \dfrac{3\cancel0}{10\cancel0} \times\dfrac{4\cancel0}{10\cancel0} \times 25000 \\ &=& \dfrac1{10} \times \dfrac2{10} \times \dfrac3{10} \times \dfrac4{10} \times 25000 \\ &=& \dfrac1{1\bcancel0} \times \dfrac2{1\bcancel0} \times \dfrac3{1\bcancel0} \times \dfrac4{10} \times 25\bcancel{000} \\ &=& (1\times2\times3\times4) \times 25 \times \dfrac1{10} \\ &=& \boxed{60} \end{aligned}$

its easy you always start form the end and work your way to the beginning

(10/100) * (20/100) * (30/100) * (40/100) * 25000 = 60

25,000 x 0.40 x 0.30 x 0.20 x 0.10 = 60