The simple interest on a certain sum of money for 2 years at 7% per annum is double the compound interest on ₹1,000 for 2 years at 10% per annum, compounded annually. What is the sum placed on simple interest?

₹3,000

With Compound interest,

Amount =  Principal × ( 1 + \(\frac{R}{100 }\))t

 = 1000 × ( 1 + \(\frac{10 }{100 }\))²

 = 1000 × \(\frac{11 }{10 }\) × \(\frac{11 }{10 }\)

= 1210

Amount = Principal + Compound Interest

Compound Interest = 1210 - 1000 = 210

Simple Interest = 2 × Compound Interest

= 2 × 210

= 420 

Now , Simple Interest = \(\frac{Principal ×Rate × Time }{100}\)

420 = \(\frac{Principal × 7 × 2 }{100}\)

Principal = Rs. 3000