6. 下图中,若三张纸条露出的部分相等,则( )纸条的长度最长。


A.甲
B.乙
C.丙

C

设露出部分长度为$a$。
甲纸条长度：$a÷\frac{1}{5}=5a$
乙纸条长度：$a÷\frac{1}{3}=3a$
丙纸条长度：$a÷\frac{1}{7}=7a$
因为$7a＞5a＞3a$，所以丙纸条最长。
C

1. 看图列式计算。(12 分)
(1)

(2)

$\frac{( )}{( )} + \frac{( )}{( )} = \frac{( )}{( )}$ ( ) $- \frac{( )}{( )} = \frac{( )}{( )}$
(3)

(4)

$\frac{1}{4} + \frac{1}{2} = $ $\frac{( )}{( )} ◯ \frac{( )}{( )} = \frac{( )}{( )}$

(1)$\frac{3}{8}+\frac{4}{8}=\frac{7}{8}$
(2)$1-\frac{8}{14}=\frac{6}{14}$
(3)$\frac{3}{4}$
(4)$\frac{4}{6}-\frac{1}{6}=\frac{3}{6}$

2. 算一算。(共 12 分)
$\begin{array}{l}$
$\frac{1}{8} + \begin{array}{|l|}$
$\hline$
$\frac{2}{8} \\$
$\hline$
$\frac{5}{8} \\$
$\hline$
$\frac{6}{8} \\$
$\hline$
$\end{array}$ = \\$$\end{array}$$\begin{array}{l}$$\frac{9}{10} - \begin{array}{|l|}$$\hline$$\frac{1}{10} \\$$\hline$$\frac{7}{10} \\$$\hline$$\frac{3}{10} \\$$\hline$$\end{array}$ = \\$
$\end{array}$

$\frac{3}{8}$ $\frac{6}{8}$ $\frac{7}{8}$ $\frac{8}{10}$ $\frac{2}{10}$ $\frac{6}{10}$

3. 计算下面各题。(共 16 分)
$\begin{array}{llll}$
$\frac{3}{6} + \frac{1}{6} = & \frac{1}{4} + \frac{3}{4} = & \frac{5}{12} + \frac{1}{12} = & \frac{7}{11} - \frac{3}{11} = \\$
$\frac{4}{5} - \frac{3}{5} = & \frac{3}{4} - \frac{1}{4} = & \frac{5}{12} - \frac{1}{12} = & \frac{5}{21} + \frac{13}{21} = \\$
$\end{array} $

$\frac{4}{6}$ $\frac{4}{4}$ $\frac{6}{12}$ $\frac{4}{11}$ $\frac{1}{5}$ $\frac{2}{4}$ $\frac{4}{12}$ $\frac{18}{21}$