登录
一、解方程。
$x+\frac {5}{13}= \frac {7}{13}$ $x-\frac {14}{3}= 3$ $1.8x÷5= 0.9$
$0.48x-7.49= 9.79$ $6.2÷4+5x= 7.2$ $(2x-6)×6= 72$
$8x-2.6x= 37.8$ $1.5×2+2x= 5$ $6x+4x= 2.9+11$
$x+\frac {5}{13}= \frac {7}{13}$ $x-\frac {14}{3}= 3$ $1.8x÷5= 0.9$
$0.48x-7.49= 9.79$ $6.2÷4+5x= 7.2$ $(2x-6)×6= 72$
$8x-2.6x= 37.8$ $1.5×2+2x= 5$ $6x+4x= 2.9+11$
答案
$x=\frac{2}{13}x=\frac{23}{3}x=2.5x=36x=1.13x=9x=7x=1x=1.39$
解析
1. $x+\frac{5}{13}=\frac{7}{13}$
解：$x=\frac{7}{13}-\frac{5}{13}$
$x=\frac{2}{13}$
2. $x-\frac{14}{3}=3$
解：$x=3+\frac{14}{3}$
$x=\frac{9}{3}+\frac{14}{3}$
$x=\frac{23}{3}$
3. $1.8x÷5=0.9$
解：$1.8x=0.9×5$
$1.8x=4.5$
$x=4.5÷1.8$
$x=2.5$
4. $0.48x - 7.49=9.79$
解：$0.48x=9.79 + 7.49$
$0.48x=17.28$
$x=17.28÷0.48$
$x=36$
5. $6.2÷4 + 5x=7.2$
解：$1.55 + 5x=7.2$
$5x=7.2 - 1.55$
$5x=5.65$
$x=5.65÷5$
$x=1.13$
6. $(2x - 6)×6=72$
解：$2x - 6=72÷6$
$2x - 6=12$
$2x=12 + 6$
$2x=18$
$x=18÷2$
$x=9$
7. $8x - 2.6x=37.8$
解：$5.4x=37.8$
$x=37.8÷5.4$
$x=7$
8. $1.5×2 + 2x=5$
解：$3 + 2x=5$
$2x=5 - 3$
$2x=2$
$x=2÷2$
$x=1$
9. $6x + 4x=2.9 + 11$
解：$10x=13.9$
$x=13.9÷10$
$x=1.39$
解：$x=\frac{7}{13}-\frac{5}{13}$
$x=\frac{2}{13}$
2. $x-\frac{14}{3}=3$
解：$x=3+\frac{14}{3}$
$x=\frac{9}{3}+\frac{14}{3}$
$x=\frac{23}{3}$
3. $1.8x÷5=0.9$
解：$1.8x=0.9×5$
$1.8x=4.5$
$x=4.5÷1.8$
$x=2.5$
4. $0.48x - 7.49=9.79$
解：$0.48x=9.79 + 7.49$
$0.48x=17.28$
$x=17.28÷0.48$
$x=36$
5. $6.2÷4 + 5x=7.2$
解：$1.55 + 5x=7.2$
$5x=7.2 - 1.55$
$5x=5.65$
$x=5.65÷5$
$x=1.13$
6. $(2x - 6)×6=72$
解：$2x - 6=72÷6$
$2x - 6=12$
$2x=12 + 6$
$2x=18$
$x=18÷2$
$x=9$
7. $8x - 2.6x=37.8$
解：$5.4x=37.8$
$x=37.8÷5.4$
$x=7$
8. $1.5×2 + 2x=5$
解：$3 + 2x=5$
$2x=5 - 3$
$2x=2$
$x=2÷2$
$x=1$
9. $6x + 4x=2.9 + 11$
解：$10x=13.9$
$x=13.9÷10$
$x=1.39$
二、计算下面各题,怎样简便就怎样计算。
$2.35×99+2.35$ $\frac {3}{7}+\frac {2}{5}+\frac {4}{7}+\frac {3}{5}$ $0.17×1.8+8.2×0.17$
$13.7×0.5-3.7÷2$ $9-\frac {4}{9}-\frac {5}{9}$ $4.58+2.39+(5.42+7.61)$
$3.72×3.5+6.28×3.5$ $\frac {7}{15}+\frac {7}{12}+\frac {8}{15}-\frac {5}{12}$ $15.4+4.7-5.4+3.3$
$(8-2.75)÷2.5+1.9$ $\frac {2}{7}+(\frac {3}{5}+\frac {1}{7})-\frac {1}{5}$ $23.25-4.75-3.25$
$2.35×99+2.35$ $\frac {3}{7}+\frac {2}{5}+\frac {4}{7}+\frac {3}{5}$ $0.17×1.8+8.2×0.17$
$13.7×0.5-3.7÷2$ $9-\frac {4}{9}-\frac {5}{9}$ $4.58+2.39+(5.42+7.61)$
$3.72×3.5+6.28×3.5$ $\frac {7}{15}+\frac {7}{12}+\frac {8}{15}-\frac {5}{12}$ $15.4+4.7-5.4+3.3$
$(8-2.75)÷2.5+1.9$ $\frac {2}{7}+(\frac {3}{5}+\frac {1}{7})-\frac {1}{5}$ $23.25-4.75-3.25$
答案
$235 2 1.75 8 2035 1\frac{1}{6} 184 \frac{29}{35} 15.25$
解析
$2.35×99+2.35$
$=2.35×(99+1)$
$=2.35×100$
$=235$
$\frac {3}{7}+\frac {2}{5}+\frac {4}{7}+\frac {3}{5}$
$=(\frac {3}{7}+\frac {4}{7})+(\frac {2}{5}+\frac {3}{5})$
$=1+1$
$=2$
$0.17×1.8+8.2×0.17$
$=0.17×(1.8+8.2)$
$=0.17×10$
$=1.7$
$13.7×0.5-3.7÷2$
$=13.7×0.5-3.7×0.5$
$=(13.7-3.7)×0.5$
$=10×0.5$
$=5$
$9-\frac {4}{9}-\frac {5}{9}$
$=9-(\frac {4}{9}+\frac {5}{9})$
$=9-1$
$=8$
$4.58+2.39+(5.42+7.61)$
$=(4.58+5.42)+(2.39+7.61)$
$=10+10$
$=20$
$3.72×3.5+6.28×3.5$
$=(3.72+6.28)×3.5$
$=10×3.5$
$=35$
$\frac {7}{15}+\frac {7}{12}+\frac {8}{15}-\frac {5}{12}$
$=(\frac {7}{15}+\frac {8}{15})+(\frac {7}{12}-\frac {5}{12})$
$=1+\frac {1}{6}$
$=1\frac {1}{6}$
$15.4+4.7-5.4+3.3$
$=(15.4-5.4)+(4.7+3.3)$
$=10+8$
$=18$
$(8-2.75)÷2.5+1.9$
$=5.25÷2.5+1.9$
$=2.1+1.9$
$=4$
$\frac {2}{7}+(\frac {3}{5}+\frac {1}{7})-\frac {1}{5}$
$=(\frac {2}{7}+\frac {1}{7})+(\frac {3}{5}-\frac {1}{5})$
$=\frac {3}{7}+\frac {2}{5}$
$=\frac {15}{35}+\frac {14}{35}$
$=\frac {29}{35}$
$23.25-4.75-3.25$
$=23.25-3.25-4.75$
$=20-4.75$
$=15.25$
$=2.35×(99+1)$
$=2.35×100$
$=235$
$\frac {3}{7}+\frac {2}{5}+\frac {4}{7}+\frac {3}{5}$
$=(\frac {3}{7}+\frac {4}{7})+(\frac {2}{5}+\frac {3}{5})$
$=1+1$
$=2$
$0.17×1.8+8.2×0.17$
$=0.17×(1.8+8.2)$
$=0.17×10$
$=1.7$
$13.7×0.5-3.7÷2$
$=13.7×0.5-3.7×0.5$
$=(13.7-3.7)×0.5$
$=10×0.5$
$=5$
$9-\frac {4}{9}-\frac {5}{9}$
$=9-(\frac {4}{9}+\frac {5}{9})$
$=9-1$
$=8$
$4.58+2.39+(5.42+7.61)$
$=(4.58+5.42)+(2.39+7.61)$
$=10+10$
$=20$
$3.72×3.5+6.28×3.5$
$=(3.72+6.28)×3.5$
$=10×3.5$
$=35$
$\frac {7}{15}+\frac {7}{12}+\frac {8}{15}-\frac {5}{12}$
$=(\frac {7}{15}+\frac {8}{15})+(\frac {7}{12}-\frac {5}{12})$
$=1+\frac {1}{6}$
$=1\frac {1}{6}$
$15.4+4.7-5.4+3.3$
$=(15.4-5.4)+(4.7+3.3)$
$=10+8$
$=18$
$(8-2.75)÷2.5+1.9$
$=5.25÷2.5+1.9$
$=2.1+1.9$
$=4$
$\frac {2}{7}+(\frac {3}{5}+\frac {1}{7})-\frac {1}{5}$
$=(\frac {2}{7}+\frac {1}{7})+(\frac {3}{5}-\frac {1}{5})$
$=\frac {3}{7}+\frac {2}{5}$
$=\frac {15}{35}+\frac {14}{35}$
$=\frac {29}{35}$
$23.25-4.75-3.25$
$=23.25-3.25-4.75$
$=20-4.75$
$=15.25$
