A man invests a certain sum of money at 6% per annum simple interest and another sum at 7% per annum simple interest. His income from interest after 2 years was Rs. 354. One-forth of the first sum is equal to one-fifth of the second sum. The total sum invested was : Pick one:
A) Rs.3100 B) Rs.2700 C) Rs.2200 D) Rs.1800 E) Rs.2100
Explanation :   Let the man invests Rs.x at 6% and Rs.y at 7%   Simple Interest on Rs.x at 6% for 2 years + Simple Interest on Rs.y at 7% for 2 years = Rs.354   x × 6 ×2 /100+y×7×2/100=354   x × 6 × 2+y×7×2=354×100   x × 6+y × 7=177×100   6x+7y=17700⋯(1)   One-forth of the first sum is equal to one-fifth of the second sum   =&gt;x/4=y/5   =&gt;x=4y/5⋯(2)   Solving (1) and (2),   6x+7y=17700   6(4y/5)+7y=17700   24y+35y=17700×5   59y=17700×   y=300×5=1500   x=4y/5   =4×1500/5   =4×300   =1200   total sum invested = x + y = 1500 + 1200= 
<gadget id="calculator">1500 + 1200</gadget>
<output>2_700</output>
2700   Answer : Option Rs.2700
<result>B</result>
A man invests a certain sum of money at 6% per annum simple interest and another sum at 7% per annum simple interest. His income from interest after 2 years was Rs. 354. One-forth of the first sum is equal to one-fifth of the second sum. The total sum invested was :