a certain sum is invested at compound interest p.a. the interest accrued in the first three years in rs 1402 and four years in rs 1834 find the rate percentage.
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8th
Maths
Comparing Quantities
Compound Interest
A certain sum is interested...
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Asked on December 26, 2019 by
Shourya Mozhi
A certain sum is interested at compound interest . The interest occurred in the first two years is Rs. 272 and that in the First three years is Rs. 434. Find the rate % ?
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ANSWER
For first two year interest =P[(1+
100
R
)
2
−1]=272 .......(1)
For first three year interest =P[(1+
100
R
)
3
−1]=434 .......(2)
On dividing equation (1) by (2), we get
⇒
(1+
100
R
)
3
−1
(1+
100
R
)
2
−1
=
434
272
Let (1+
100
R
)=x ...........(3)
⇒
(x
3
−1)
(x
2
−1)
=
217
136
⇒
(x
2
+x+1)
(x+1)
=
217
136
136x
2
−81x−81=0
After solving x will be 1.1248
By putting this value in eq (3), we get
R=12.48 approx 12.50 %