Question

The compound interest on a certain sum at a certain
rate of interest for the second year is 7680 and
for the third year is 9216. What will be the simple
interest on the same sum at the same rate to 4.5 year?​

Answer 1

Answer:

simple interest SI= Rs.15709.09

Step-by-step explanation:

Answer 2

The simple interest will be Rs 4800

Step-by-step explanation:

Let rate of interest compounded annually be r and sum be p

Formula:- $A=p(1+r)^t$

where, A is amount , p is sum, r is rate of interest and t is time.

• The compound interest on a certain sum at a certain  rate of interest for the second year is 7680

Therefore, $7680=p(1+r)^2$--------------(1)

• The compound interest on a certain sum at a certain  rate of interest for the third year is 9216

Therefore, $9216=p(1+r)^3$--------------(2)

Divide eq(2) by eq(1)

$\dfrac{9216}{7680}=1+r$

$r=20\%$

Put r into eq(1)

$7680=p(1+\frac{20}{100})^2$--------------(1)

$p=\dfrac{7680}{(1+\frac{20}{100})^2}$

$p=\dfrqac{16000}{3}$

Now calculate simple interest on the same sum at same rate of interest to 4.5 years.

Formula:- $SI=prt$

where, SI is simple interest,

p is sum, p=16000/3

r is rate, r =20%

t is time, t = 4.5 years

Substitute the value into formula

$SI=\dfrac{16000}{3}\times \dfrac{20}{100}\times 4.5$

$SI=4800$

Hence, the simple interest will be Rs 4800

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