The maturity value of rd account is 16176
Monthly instalment is 400
Rate of interest 8%
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ANSWER
Monthly instalment, P=Rs. 400
number of months=n
Rate of interest, r=8%
Simple interest, ∫I=P×
2×12
n(n+1)
×
100
r
=400×
100
8
×
24
n(n+1)
=
3
4
n(n+1)
Given, maturity value of RD account =Rs. 16,176
⇒400×n+
3
4
n(n+1)=16,176
⇒400n+
3
4
n
2
+
3
4
n=16176
⇒
3
4
n
2
+
3
4
n+400n−16176=0
⇒4n
2
+4n+1200n−48528=0
⇒4n
2
+1204n−48528=0
⇒4(n
2
+301n−12132)=0
⇒n
2
+301n−12132=0
⇒n
2
+337n−36n−12132=0
⇒n(n+337)−36(n+337)=0
⇒(n−36)(n+337)=0
⇒n=36 or n=−337, which is neglected since number of months cannot be negative.
Hence time period of RD account =36 months =3 years.
solution
December 20, 2019
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A sum of money becomes
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41
of itself in
4
1
years at a certain rate of simple interest. What is the rate of interest per annum
1 Verified Answer
Find the interest on Rs. 1200 for 4 years at the rate of 6
2
1
% per annum.
Monthly instalment, P=Rs. 400
number of months=n
Rate of interest, r=8%
Simple interest, ∫I=P×
2×12
n(n+1)
×
100
r
=400×
100
8
×
24
n(n+1)
=
3
4
n(n+1)
Given, maturity value of RD account =Rs. 16,176
⇒400×n+
3
4
n(n+1)=16,176
⇒400n+
3
4
n
2
+
3
4
n=16176
⇒
3
4
n
2
+
3
4
n+400n−16176=0
⇒4n
2
+4n+1200n−48528=0
⇒4n
2
+1204n−48528=0
⇒4(n
2
+301n−12132)=0
⇒n
2
+301n−12132=0
⇒n
2
+337n−36n−12132=0
⇒n(n+337)−36(n+337)=0
⇒(n−36)(n+337)=0
⇒n=36 or n=−337, which is neglected since number of months cannot be negative.
Hence time period of RD account =36 months =3 years.