Question

What is the rate of interest (in %) if simple interest earned on a certain sum for the 3rd year is Rs. 20 and compound interest earned in 2 years is Rs. 41.6? ​

Answer 1

Answer:

I hope it helps

Step-by-step explanation:

Let the principle is P Rs. and rate of interest is R%

Time =2 years

Then for C.I:

CI=P(1+

100

R

)

2

−P

⇒41=P[(1+

100

R

)

2

−1] .....[∵(a+b)

2

=a

2

+b

2

+2ab]

⇒41=P[1+

100

2R

+

10000

R

2

−1]

⇒41=

100

2PR

+

10000

PR

2

⇒41=

50

PR

+

10000

PR∗R

........(1)

For SI:

⇒SI=

100

PRT

⇒40=

100

PR2

⇒40=

50

PR

⇒PR=2000

Put the value of PR in (1),

41=

50

2000

+

10000

2000

×R

⇒41=40+

5

1

R

⇒41−40=

5

1

R

⇒R=1×5

⇒R=5%