The usual way to find the compound interest is given by the formula A = .p(1+r/100)^n
In this formula,
A is the amount at the end of the period of investment
P is the principal that is invested
r is the rate of interest in % p.a
And n is the number of years for which the principal has been invested.
In this case, it would turn out to be A =1500(1+20/100)^3
= 2592.
I. gives, Rate = 5% p.a.
II. gives, S.I. for 1 year = Rs. 600.
III. gives, sum = 10 x (S.I. for 2 years).
Now I, and II give the sum.
For this sum, C.I. and hence amount can be obtained.
Thus, III is redundant.
Again, II gives S.I. for 2 years = Rs. (600 x 2) = Rs. 1200.
Now, from III, Sum = Rs. (10 x 1200) = Rs . 12000.
Thus,Rate = =5%
Thus, C.I. for 2 years and therefore, amount can be obtained.
Thus, I is redundant.
At first glance it might seem that this problem cannot be solved because we do not have enough
information. It can be solved as long as you double whatever amount you start with. If we start with
$100, then P = $100 and FV = $200.
FV=P(1+r/n)^nt
Given,
Compound rate, R = 10% per annum
Time = 2 years
C.I = Rs. 420
Let P be the required principal.
A = (P+C.I)
Amount, A =
(P+C.I) =
(P+420) = P[11/10][11/10]
P-1.21P = -420
0.21P = 420
Hence, P = 420/0.21 = Rs. 2000
Amount =
= 8000 x 21/20 x 21/20
= Rs. 8820
t=3
FV=P(1+r/n)^nt
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