已选分类
理学数学
应用题
应用题
单选题甲、乙两人同时从同一地点出发，相背而行．1小时后他们分别到达各自的终点A和B．若从原地出发，互换彼此的目的地，则甲在乙到达A之后35分钟到达B．问甲的速度和乙的速度之比是( )． A.3:5 B.4:3 C.4:5 D.3:4 E．以上结论均不正确
单选题A square countertop has a square tile inlay in the center, leaving an untiled strip of uniform width around the tile. If the ratio of the tiled area to the untiled area is 25 to 39, which of the following could be the width, in inches, of tile strip? Ⅰ.1 Ⅱ.3 Ⅲ.4 (A) Ⅰ only (B) Ⅱ only (C) Ⅰ and Ⅱ only (D) Ⅰ and Ⅲ only (E) Ⅰ, Ⅱ, and Ⅲ
单选题设矩阵的秩为2，则______。A.a=0，b=0B.a=0，b≠0C.a≠0，b=0D.a≠0，b≠0
单选题设xlny=ylnx确定函数y=y(x)，则______．A．-1B．-1+eC．1D．1+e
单选题In1960,thenumberofstudentsenrolledatacollegewas500.In1980,thenumberofstudentsenrolledatthecollegewastimesasgreatasthatin1960.Whatwasthenumberofstudentsenrolledatthecollegein1980?(A)1,750(B)1,250(C)1,000(D)500(E)250
单选题The width of a rectangle is 6 cm less than the length. If the perimeter of the rectangle is 48 cm, what is the length of the rectangle in centimeters? (A) 48 (B) 15 (C) 12 (D) 9 (E) 6
单选题Ifthevariables,X,Y,andZtakeononlythevalues10,20,30,40,50,60,or70withfrequenciesindicatedbytheshadedregionsabove,forwhichofthefrequencydistributionsisthemeanequaltothemedian?(A)Xonly(B)Yonly(C)Zonly(D)XandY(E)XandZ
单选题
单选题设，则______．A．-1B．1C．ln2D．
单选题Alaborerispaid$8perhourforan8-hourdayandtimesthatrateforeachhourinexcessof8hoursinasingeday.Ifthelaborerreceived$80forasingleday'swork,howlongdidheworkonthatday?(A)6hr.40min.(B)9hr.20min.(C)9hr.30min.(D)9hr.40Min.(E)10hr.
单选题
单选题3x2+bx+c=0(c≠O)的两个根为a、β如果又以a+β、aβ为根的一元二次方程是3x2-bx+c=0，则b和c分别为( )． A．2，6 B．3，4 C．-2，-6 D．-3，-6 E．以上结果都不正确
单选题Joe works two part time jobs. One week Joe worked 8 hours at one job, earning $150, and 4.5 hours at other job, earning $90. What were his average hourly earnings for the week?
单选题在x=0处可导，则______．
单选题已知-2x2+5x+c≥0的解为则c为()．
单选题一个数为两个三位数之和，问其百位数是否为这两个三位数百位数之和? (1)此数的十位数为两个数的十位数之和； (2)此数的个位数为两个数的个位数之和。 (A) 条件(1)充分，但条件(2)不充分． (B) 条件(2)充分，但条件(1)不充分． (C) 条件(1)和(2)单独都不充分，但条件(1)和条件(2)联合起来充分． (D) 条件(1)充分，条件(2)也充分． (E) 条件(1)和条件(2)单独都不充分，条件(1)和条件(2)联合起来也不充分．
单选题设，则y3y″=______．A．2B．1C．-1D．-2
单选题一项复印工作，如果由复印机A，B单独完成，分别需50分钟，40分钟．现两台机器同时工作了20分钟，B机器损坏需维修，余下的工作由A机器单独完成，则完成这项复印工作共需时间( )． A．10分钟 B．15分钟 C．18分钟 D．20分钟 E．25分钟