Question

The compound interest on certain sum of money at the certain rate for 2 years is 40.80 and the simple interest on the same sum is 40 at the same rate and same time. Find the rate of interest
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Answer 1

Let :-

• The sum of money be P

To Find :-

• The rate of interest = ?

Solution :-

• To calculate the rate of interest at first we have to set up equation by helping clue in the given Question

Calculation for 1st equation :-

• CI = ₹ 40.80. T = 2 years. R = r%

⇒ CI = P(1 + r/100)^t - P

⇒ 40.80 = P(1 + r/100)² - P

⇒ 40.80 = P(100 + r/100)² - P

⇒ 40.80 = P(100 + r)²/10000 - P

⇒ 40.80 = P(10000 + 200r + r²)/10000 - P

⇒ 40.80 = (10000P + 200Pr + Pr²)/10000 - P

⇒ 40.80 = 10000P + 200Pr + Pr² - 10000P/10000

⇒ 40.80 = (200Pr + Pr²)/10000

⇒ 200Pr + Pr² = 408000 ----------(i)

Calculation for 2nd equation :-

• SI = ₹ 40. Time = 2years. R = r%

⇒ SI = P × T × R/100

⇒ 40 = P × 2 × r/100

⇒ 40 = Pr/50

⇒ Pr = 2000-------(ii)

• Now putting the value of Pr in eq (i) :-]

⇒ 200Pr + Pr² = 408000

⇒ Pr(200 + r) = 408000

⇒ 2000(200 + r) = 408000

⇒ 400000 + 2000r = 408000

⇒ 2000r = 408000 - 400000

⇒ 2000r = 8000

⇒ r = 4%

Hence, the required rate of interest = 4%

Answer 2

Answer:

$\sf\tt\large{\green {\underline {\underline{⚘\;Question:}}}}$

The compound interest on certain sum of money at the certain rate for 2 years is 40.80 and the simple interest on the same sum is 40 at the same rate and same time .Find the rate of interest.

$\sf\tt\large{\green {\underline {\underline{⚘\;Answer:}}}}$

rate of interest = 4%.

$\sf\tt\large{\red {\underline {\underline{\;Solution:}}}}$

Hey mate ,

First let verify your question and later on enter to calculations.

In the question given that the compound interest on certain sum of money at a certain rate for 2 years is 40.80 and simple interest on the same sum is 40 at the same rate and same time.

Here we want to calculate the rate of interest of the compound.

Here,

kindly refer the above given attachment for more information.

Hope it helps u mate .

Thank you .