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A reduction of 20% in the price of rice enables a customer to purchase 4kg more for Rs.120. Then find original price of rice per kg
$$4$$ kg$$\rightarrow$$ Rs.$$120$$
then $$1$$kg $$\rightarrow$$ Rs.$$\Large\frac{120}{4}$$ $$=$$ Rs.$$30$$
Reduced price: $$30$$ $$\times$$ $$\Large\frac{20}{100}$$ $$=$$ Rs.$$6$$/kg
Original price: $$6$$ $$\times$$ $$\Large\frac{100}{(100-20)}$$ $$=$$ $$6$$ $$\times$$ $$\Large\frac{100}{80}$$ $$=$$ Rs.$$7.50$$/kg
The time required for a sum of money to become 31 times of itself at 15% Simple Interest per annum is?
Let the principal be Rs.P
Let the time period be x years
Then, After x years, P will become Rs.31P
⇒ Interest = 31P - P = Rs.30P
⇒ $$\dfrac{P \times 15 \times x}{100} = 30P$$
⇒ x = 200
Hence, After 200 years, the sum of money will become 31 times of itself.
A trader mixes 20 kg of rice at Rs.15 per kg with 25 kg of rice at Rs.20 per kg and sells the mixture at Rs.24 per kg. Then find his profit/loss percent.
Cost Price of 45 kg of rice $$= 20\times15+25\times20 = 300+500 = Rs.800$$
Selling Price of 45 kg of rice $$= 45\times24 = Rs.1080$$
Profit = 1080-800 = Rs.280
Profit percentage = $$\dfrac{280}{800}\times100 = 35$$
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