A sum was invested on simple interest at a certain rate

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A sum was invested on simple interest at a certain rate for 2 years. Had it been put at 3% higher rate, it would have fetched ₹72 more. The sum is

Let the sum = P and original rate = R% per annum.
Then,
According to question ,

P × (R + 3) × 2	-	P × R × 2	= 72
100		100

⇒	P × 3 × 2	= 72
	100

⇒ P =	72 × 100	= ₹ 1200
	3 × 2

Second method to solve this question :
Here , P₁ = P, R₁ = R, T₁ = 2
P₂ = P, R₂ = R + 3, T₂ = 2 , S.I.= 72

∴ SI =	P₂ × R₂ × T₂ - P₁ × R₁ × T₁
	100

72 =	P × (R + 3) × 2 - P × R × 2
	100

7200 = 6P
P = ₹ 1200