tailieunhanh - Master the Gre 2010 - Part 28

Peterson's Master the Gre 2010 - Part book includes 9 full-length practice tests , thorough reviews of every section on the exam, and expert tips and strategies from a test prep pro. GRE (Graduage Record Examination General Test) is a commercially-run standardized test and an admission requirement for many graduate schools in USA and other English-speaking countries. GRE can earn you between 200-800 points. | Chapter 10 Math Review Number Theory and Algebra 253 34. Dr. Kramer plans to invest 20 000 in an account paying 6 interest annually. How much more must she invest at the same time at 3 so that her total annual income during the first year is 4 of her entire investment A 32 000 B 36 000 C 40 000 D 47 000 E 49 000 The correct answer is C . Letting xequal the amount invested at 3 you can express Dr. Kramer s total investment as 20 000 x. The interest on 20 000 plus the interest on the additional investment equals the total interest from both investments. You can state this algebraically as follows 20 000 20 000 X Multiply all terms by 100 to eliminate decimals then solve for x. 6 20 000 3x 4 20 000 x 120 000 3x 80 000 4x 40 000 x She must invest 40 000 at 3 for her total annual income to be 4 of her total investment 60 000 . Beware In solving GRE investment problems by all means size up the question to make sure your calculated answer is in the ballpark. But don t rely on your intuition to derive a precise solution. Interest problems can be misleading. For instance in attempting to solve the previous problem you might have guessed that Dr. Kramer would need to invest more than twice as much at 3 than at 6 to lower the overall interest rate to 4 which is not true. Problems of Rate of Production and Rate of Travel A rate is a fraction that expresses a quantity per unit of time. For example the rate at which a machine produces a certain product is expressed this way number of units produced rate of production ------------------------ time RATE OF PRODUCTION WORK A simple GRE rate question might provide two of the three terms and then ask you for the value of the third term. To complicate matters the question might also require you to convert a number from one unit of measurement to another. 254 PART IV Quantitative Reasoning 35. If a printer can print pages at a rate of 15 pages per minute how many pages can it print in 2- hours pages .