帮我解答并分析试卷的答案---**Header:** * 神龙教育 非常 海淀单元测试AB卷 素质过关A卷 (Shenlong Education Very Haidian Unit Test AB Paper Quality Assessment A Paper) * 数学五年级 下 RJ (Mathematics Grade 5, Lower Semester, Ren Jiaoban - likely a textbook version) * 时间: 90 分钟 (Time: 90 minutes) * 满分: 100 分 (Full Score: 100 points) * 加星题目讲解 (Starred questions explained) * 等级 (Level) **Student Information:** * 姓名 (Name) * 班级 (Class) * 学号 (Student ID) **Section 1: 基础知识达标 (Basic Knowledge Standard)** **细心填空。(每空1分,共23分)** (Fill in the Blanks. 1 point per blank, total 23 points) 1. ( ) ÷ 2 = ( )/40 = 72/( ) = 0.8 2. 12和18的最大公因数是( ),最小公倍数是( )。 3. 把4米长的绳子平均分成7段,每段占全长的( ),每段长( )米。 4. 3.02 dm³ = ( ) cm³ 7500 dm³ = ( ) m³ 846 mL = ( ) L 9.78 dm³ = ( ) L ( ) mL 5. 用5个小正方体搭一个几何体,从左面和正面看到的图形都是 [Image of a 1x2 rectangle composed of two squares], 共有( )种搭法。 * *Image Description:* A simple diagram showing a rectangle made of two adjacent squares. This shape is seen from the left and front views. 6. 比较大小。(填“>”“<”或“=”)(Compare size. Fill in ">", "<", or "=") * 3/7 ○ 5/9 * 5/6 ○ 7/8 * 7/12 - 1/4 ○ 1/4 * 2/3 + 2/5 ○ 4/5 + 1/3 7. 把2/7的分母扩大到原来的4倍,要使分数的大小不变,分子应加上( )。 8. 一个棱长总和是84 cm 的正方体的体积是( )cm³。 9. 一个长方体长8 cm,宽6 cm,高5 cm,把它锯成两个形状完全相同的长方体,表面积最少增加( )cm²。 10. 有13盒饼干,其中12盒质量相同,另有1盒少了几块,如果用天平称,至少称( )次才能保证找到质量轻的那盒饼干。 11. 一个长方体纸盒,从里面量,长6 dm,宽4 dm,高7 dm,若把棱长为2 dm 的正方体积木装进盒内(不外露),最多能装( )块。 12. 哈尔滨冰雪大世界主体建筑是冰晶宫,里面每天都有精彩节目上演。冰晶宫中有一块长60 dm,宽36 dm 的长方形空地。如果用同样大小的正方形冰砖铺地而没有剩余,正方形冰砖的边长最大是( )dm。 **Section 2: 准确判断。(对的画“√”,错的画“×”)(5分)** (Accurate Judgement. Mark "√" for correct, "×" for incorrect) (5 points) 1. 大于3/11而小于5/11的真分数有无数个。( ) 2. 如果9/a是一个能化成整数的假分数,那么a是9的因数。( ) 3. 如果a、b是互质数,那么它们的最小公倍数是ab。( ) **Section 3: 择优选择。(把正确答案的序号填在括号里)(10分)** (Optimal Selection. Fill the number of the correct option in the parenthesis) (10 points) 1. 如图,它可以看作是由一个平行四边形通过旋转得到的,每次旋转( )。 * *Image Description:* A diagram showing a three-bladed shape resembling a propeller, where each blade is a rhombus. The blades originate from a central point and are rotationally symmetric. * A. 60° * B. 90° * C. 120° 2. 数学课上,明明用学具棒搭一个长方体框架,搭了其中的三根,就能决定这个长方体的形状与大小的是( )。 * *Image Description:* * A. An L-shaped figure formed by two perpendicular line segments, with one segment extending beyond the vertex. * B. A single straight line segment. * C. A right angle formed by two perpendicular line segments meeting at a vertex. * A. [Image A described above] * B. [Image B described above] * C. [Image C described above] 3. 有一个长5分米,宽和高都是3分米的长方体硬纸箱,如果用绳子将纸箱按照右图所示捆扎起来,打结处需2分米绳子,共需绳子( )分米。 * *Image Description:* A diagram showing a rectangular prism box tied with rope. The rope configuration wraps around the box such that it covers two pairs of opposite faces (length and height, width and height). The top face is shown divided into a 2x2 grid. The height of the box is labeled 15 cm in a separate adjacent diagram which seems to be related to Question 4, not Question 3's diagram. The diagram for Question 3 shows a box with dimensions likely 5 dm (length), 3 dm (width), and 3 dm (height). The rope goes twice around the length and height, and twice around the width and height. * A. 21 * B. 36 * C. 42 4. (★★★) 把3个相同的小长方体拼成1个15 cm 高的大长方体,表面积减少了48 cm²,那么原来1个小长方体的体积是( )cm³。 * *Image Description:* A diagram showing three identical rectangular prisms stacked vertically on top of each other. The total height of the stacked prisms is labeled 15 cm. A single rectangular prism is shown next to the stack, with its height labeled 15 cm. (Note: The diagram for Q4 appears to be using 15cm as the height of the combined large box, not necessarily the individual boxes as implied by the arrangement; however, the text says the *large* box is 15cm high). Let's assume the stack's total height is 15 cm, so each small box is 15/3 = 5 cm high. * A. 180 * B. 120 * C. 60 5. 暑假里,学校足球队李老师用打电话的方式通知10名同学参加训练,每分钟通知1人,最少花( )分钟就能通知完。 * A. 10 * B. 4 * C. 5 **Section 4: 仔细计算。(24分)** (Careful Calculation. 24 points) **1. 直接写得数。(4分)** (Directly write the answer. 4 points) * 1/3 + 1/4 = * 3/8 + 3/8 = * 1 - 1/2 = * 2/3 + 1/3 = * 1/12 + 7/12 = * 1/7 - 1/8 = * 5/9 + 2/9 = * 2/3 + 4/9 + 1/3 = * 5/8 - 1/8 - 3/8 = **2. 解方程。(8分)** (Solve the equations. 8 points) * x - 8/15 = 2/5 * 1/5 + x = 9/20 * 5/6 + x = 7/2 * x - 4/7 = 2 1/2 **3. 脱式计算。(能简算的要简算)(12分)** (Step-by-step calculation. Simplify if possible) (12 points) * 5/6 - (2/3 - 1/8) * 13/12 - 3/8 - 5/8 * 5/6 - 3/4 + 1/6 - 1/4 **Footer:** * 数学五年级 下 RJ 39 (Mathematics Grade 5, Lower Semester, RJ, Page 39)