Question

In a certain time, a sum becomes 4 times at the rate of 5% per annum. At what rate of simple interest, the same sum becomes 8 times in the same duration?​

Answer 1

Answer:

Let 100 was the Sum.

Amount = 400.

Interest = 300.

R = 5%.

Time = T (Let).

Interest = PTR/100 = (100 *T *5)/100.

500T /100 = 300

5T = 300

T = 60 years.

Now for second case,

Let rate = r.

Time = 60 years.

Amount = 800.

Interest = 700.

Now,

I = PTr/100

700 = 100*60 *r/100

60r = 700

r = 70/6 = 11.66%.

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Answer 2

Answer:

11.66%

Step-by-step explanation:

Let the time taken=T

Let the sum=P

amount=4*P(as per the question amount is four times principle)=4P

r=5%

SI=amount-P

    =4P-P

    =3P

SI=P*r*T/100

3P=P*5*T/100

P willget cancelled

3=5*T/100

T=3*20

   =60years

SECOND PART

now,T=60yrs

        P=P

       amount=8P

      SI=amount-P

         =8P-P=7P

therefore, SI=7P

SI=P*T*r/100

7P=P*60*r/100

P will get cancelled

7=1*60*r/100

r=7*100/60

r=35/3=11.66%

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