A total of $20,000 was invested in two certificates of deposit at simple annual interest rates of 6 percent and 9 percent, respectively. If the total interest on the two certificates was $1,440 at the end of one year, what fractional part of the $20.000 was invested at the higher rate?  Answers:  A) 11 / 20  B) 2 / 5  C) 1 / 2  D) 3 / 5  E) 3 / 4

Rationale: x * 6 / 100 * 1 + ( 20000 - x ) * 9 / 100 * 1 = 1440 6 x - 8 x = 144000 - 180000 = > - 2 x = - 18000 = > x = 9000 so 11000 / 20000 = 11 / 20 answer - a
Answer: A