A sum of ₹10000 is invested in three schemes of simple interest. The annual interest rates are respectively, 4%, 6% and 10%. ₹4000 were invested in the first scheme. If the total interest earned after five years is ₹2800, then how much money was invested in the third scheme?

₹1000

Let Sum invested in 2nd scheme  = x

Sum invested in 3rd scheme = ( 6000 - x )

By using formula , 

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

\(\frac{4000 ×4 × 5 }{100}\)  +  \(\frac{x ×6 × 5 }{100}\) +

\(\frac{(6000-x) ×10× 5 }{100}\) = 2800

800 + \(\frac{x × 3 }{10}\) +\(\frac{(6000-x) × 5 }{10}\) = 2800

 \(\frac{3x }{10}\) + \(\frac{30000 - 5x  }{10}\)  = 2000

3x + 30000 - 5x = 20000

-2x = - 10000

x = 5000

Amount invest in 2nd scheme = 5000

So , Amount invested in 3rd scheme = 6000 - 5000 = 1000