John invested a sum of money at an annual simple interest

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John invested a sum of money at an annual simple interest rate of 10%. At the end of four years the amount invested plus interest earned was ₹ 770. The amount invested was

If the principal be p, then Simple interest = (770 – p)

∴ Principal =	SI × 100
	Time × Rate

p =	(770 - p) × 100
	4 × 10

⇒ 2p = (770 – p) × 5
⇒ 2p + 5p = 770 × 5
⇒ 7p = 770 × 5

∴ p =	770 × 5
	7

p = ₹ 550