Question

the difference between compound interest and simple interestfor two is rs 80 when rate of interest is 4 percent per annum find the sum of money​

Answer 1

Answer:

Let the rate per cent p.a.be r. Then,

S.I.=Rs.(5000×

100

r

×2)=Rs.100r

C.I.=Rs.

⎣

⎢

⎡

5000(1+

100

r

)

2

−5000

⎦

⎥

⎤

=Rs.5000

⎣

⎢

⎡

(1+

100

r

)

2

−1

⎦

⎥

⎤

=Rs.5000[(1+

10000

r

2

+

100

2r

)−1]

=Rs.5000(

10000

r

2

+

50

r

)=Rs.

10000

5000(r

2

+200r)

=Rs.(

2

r

2

+100r)

∴C.I.−S.I.=72

⇒

2

r

2

+100r−100r=72

⇒

2

r

2

=72

⇒r

2

=144

⇒r=12%p.a.