Re: [計量] 好多題計量請教

看板GRE (GRE入學考試)作者herbert570 (エニシ縁)時間15年前 (2011/02/09 23:44)推噓1(1推 0噓 0→)

留言1則, 1人參與討論串24/26 (看更多)

※ 引述《balance9235 (退伍變米蟲)》之銘言： : 1. Mr. Smith invested part of his 40,000USD investment in high yield bonds at : 19/2% (原本是帶分數，九又二分之一), and preferred stocks at 8%. If his : annual income from both investments is 3,620USD, how much did he invest in : the bonds and in the stocks? : ANS:bonds:28,000 stocks:12,000 high yield bonds: x preferred stocks: y x+ y = 40000 0.095x+ 0.08y = 3620 =>0.015x = 3620-3200 = 420 x = 28000 => y = 12000 : 2. How many ounces of an alloy containing alloy containing 35% aluminum must : melted with an alloy containing 65% aluminum to obtain 30 ounces of a alloy : containing 55% aluminum? : ANS:35%:10oz. 65%:20oz. 65-35=30 切成6等分後一分為5 50% 是 3/6的65% 和 3/6的35% 所以55% 就是 4/6的65% 和 2/6的35% 因此35%佔三分之一，也就是10oz 65%佔三分之二，也就是20oz : 3. How amny quarts of pure water must be added to 15 quarts of a solution : that is 15% acid in order to dilute it to a solution that is 12% acid? : ANS:15/4 quarts. (15*15%)/(15+x)=12% 15+x=225/12 x=45/12=15/4 : 4. Two pipes can fill a tank in 10 hours and 12 hours respectively. A third : pipe can drain the tank in 20 hours. How long will it take to be filed : if all three pipes are open? : ANS:7.5 hr rate=1/10+1/12+1/20=(6+5+3)/60=7/30 =>30/7 不知道是不是我有誤解題目... : 5. A financial constant invest 6,000USD at a certain rate and 8,000USD at a : rate that is 1% less than twice the rate at 6,000USD. If the total income : from both investment is 1,240USD. What is the rate of each investment? : ANS:6,000 at 6%. 8,000 at 11%. 6000x+8000y=1240 y=2x-0.01 =>22000x-80=1240 22000x=1320 x=1320/220 % =6% y=11% : 6. 溶液K的鹽濃度5%(體積)，問多少升的3.5%溶液加入溶液K500升之後，總濃度變成4%? : ANS:1000升 5%佔三分之一，3.5%佔三分之二所以3.5%是5%的兩位，為1000升 : 7.15%換成圓心角是多少度? : ANS:54度 360*15/100=54 : 8. 納稅額為1050，加上對超出30,000的部分徵6%的稅，某人納稅額為其收入的4%，其收 : 入為多少？與30,000比。 : ANS:不知道怪怪的...依題目感覺是1050/0.04就得到答案了...不會不知道啊..... 1050/0.04=1050*25=26250 : 9. K^K = K，比較K和2的大小。 : ANS:小於 K=1是唯一解 : 10. 一項體育運動原先的紀錄是6 feet，新記錄提高到6 feet 2 inch，問原先記錄對新 : 記錄的比例與0.95誰比較大？ (1 feet = 12inch) : ANS:前者大六又十二分之二 feet=37/6 37/6*19/20=703/120 < 720/120 所以前者大 -- -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 218.169.178.121