Question

9. A reduction of 20% in sugar price enables one to get 4 kg sugar more for Rs.
160. What was the original price of sugar?


10. A certain sum of money doubles itself in 12 years. In how many years will
it treble itself by simple interest?

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Answer 1

Answer:

Question 9).

Let the original Price of sugar be x

the original Quantity of sugar be y

xy = 160 ...........(1)

According to the question,

$(x-\frac{20}{100}x)(y+4)=160$

$xy-\frac{20}{100}xy+4x-\frac{20\times4}{100}x=160$

$160-\frac{1}{5}\times160+4x-\frac{4}{5}x=160$

$-32+\frac{16x}{5}=0$

16x/5 = 32

x = 2 × 5

x = 10

Therefore, Original Price of Sugar is Rs. 10

Question 10).

let x be the amount

So, P = x

T = 12 years

A = 2x

SI = 2x - x = x

Using SI formula,

$SI=\frac{P\times R\times T}{100}$

$x=\frac{x\times R\times12}{100}$

R = 100/12 %

Now, when amount is tripled,

we have A = 3x

P = x

R = 100/12 %

SI = 3x - x = 2x

We have to find Time , T

$SI=\frac{P\times R\times T}{100}$

$2x=\frac{x\times\frac{100}{12}\timesT}{100}$

T = 2 × 12

T = 24 years

Therefore, In 24 years It will be tripled.