At the beginning of 2011, Albert invests $15,000 at 10% simple annual interest, $6,000 at 7% simple annual interest, and $x at 8% simple annual interest. If, by the end of 2011, Albert receives interest totaling 9% of the sum of his three investments, then the ratio of $x to the sum of his two other investments is  Choose the most appropriate option: A) 1 : 3 B) 1 : 4 C) 1 : 6 D) 1 : 7 E) 1 : 8
Total interest earned = (10/100)*15000 + (7/100)*6000 + (8/100)*x = (192,000+8x)/100   Also, Total interest earned = (9/100)*(15000 + 6000 + x) = (9/100)*(21000 + x)   i.e. (9/100)*(21000 + x) = (192,000+8x)/100   i.e. 189,000 + 9x = 192,000+8x   i.e. x = 3000   Required ratio = x / (15000 +6000) = 3000 / 21000 = 1/7   Answer: option 1 : 7
<result>D</result>
At the beginning of 2011, Albert invests $15,000 at 10% simple annual interest, $6,000 at 7% simple annual interest, and $x at 8% simple annual interest. If, by the end of 2011, Albert receives interest totaling 9% of the sum of his three investments, then the ratio of $x to the sum of his two other investments is