At the rate of simple interest per annum, the interest on

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At the rate of simple interest per annum, the interest on a certain sum of money for 10 years will be 2 5 th part of the amount, then the rate of simple interest is

As per the given in question ,

Amount after 10 years = P		1 +	RT		= P		1 +	R × 10
			100					100

Amount = Rs. P		1 +	R
			10

∴ Simple Interest = Rs. P		1 +	R		×	2
			10			5

∴ Rate =	Simple Interest × 100
	Principal × Time

⇒ R = 4		1 +	R
			10

⇒	R	= 1 +	R
	4		10

⇒	R	-	R	= 1
	4		10

∴	5R - 2R	= 1
	20

⇒ 3R = 20

⇒ R =	20	= 6	2	%
	3		3

Second method to solve this question :

Here, S.I. =	2	amount
	5

S.I. =	2	(P + S.I.)
	5

⇒ S.I. =	2	S.I. +	2	P
	5		5

⇒	3	S.I. =	2	P
	5		5

S.I. =	2	P
	3

Now, n =	2	, T = 10 years.
	3

⇒ R =	n × 100
	T

R =	2	×	100
	3		10

R =	20	= 6	2	%
	3		3