A person deposited 400 Rs. for 2 years, 550 Rs. for 4 years and 1200 Rs. for 6 years. He received the total simple interest of 1020 Rs. The rate of interest per annum is :
[A]5%
[B]10%
[C]15%
[D]20%

10%
Let the rate of interest be R per cent per annum.
\therefore \frac{400\times 2\times R}{100}+\frac{500\times 4\times R}{100} + \frac{1200\times 6\times R}{100} = 1020
=> 8R+22R+72R = 1020
=> 102R = 1020
=> R = \frac{1020}{102} = 10\%
Hence option [B] is correct answer.