1. 在$〇$里填上运算符号,在$□$里填上合适的数。
(1) $3x + 7 = 25$
解:$3x + 7$
$3x =$
$3x$
$x =$
(2) $2(x - 9) = 36$
解:$2(x - 9)$
$x - 9 =$
$x - 9$
$x =$
(1) $3x + 7 = 25$
解:$3x + 7$
-
7
$= 25$-
7
$3x =$
18
$3x$
÷
3
$=$18
÷
3
$x =$
6
(2) $2(x - 9) = 36$
解:$2(x - 9)$
÷
2
$= 36$÷
2
$x - 9 =$
18
$x - 9$
+
9
$=$18
+
9
$x =$
27
答案:
1.
(1)- 7 - 7 18 ÷ 3 18 ÷ 3 6
(2)÷ 2 ÷ 2 18 + 9 18 + 9 27
(1)- 7 - 7 18 ÷ 3 18 ÷ 3 6
(2)÷ 2 ÷ 2 18 + 9 18 + 9 27
2. 解下列方程。
$4x - 13 = 23$ $x - 0.45x = 11$
$92 - 7x = 50$ $2(x - 5) = 24$
$4x - 0.4×8 = 7.2$ $(2x + 3)÷6 = 5$
$4x - 13 = 23$ $x - 0.45x = 11$
$92 - 7x = 50$ $2(x - 5) = 24$
$4x - 0.4×8 = 7.2$ $(2x + 3)÷6 = 5$
答案:
2.x=9 x=20 x=6 x=17 x=2.6 x=13.5
解:$4x - 13 = 23$
$4x = 23 + 13$
$4x = 36$
$x = 9$
$x - 0.45x = 11$
$0.55x = 11$
$x = 11÷0.55$
$x = 20$
$92 - 7x = 50$
$7x = 92 - 50$
$7x = 42$
$x = 6$
$2(x - 5) = 24$
$x - 5 = 24÷2$
$x - 5 = 12$
$x = 17$
$4x - 0.4×8 = 7.2$
$4x - 3.2 = 7.2$
$4x = 7.2 + 3.2$
$4x = 10.4$
$x = 2.6$
$(2x + 3)÷6 = 5$
$2x + 3 = 5×6$
$2x + 3 = 30$
$2x = 27$
$x = 13.5$
解:$4x - 13 = 23$
$4x = 23 + 13$
$4x = 36$
$x = 9$
$x - 0.45x = 11$
$0.55x = 11$
$x = 11÷0.55$
$x = 20$
$92 - 7x = 50$
$7x = 92 - 50$
$7x = 42$
$x = 6$
$2(x - 5) = 24$
$x - 5 = 24÷2$
$x - 5 = 12$
$x = 17$
$4x - 0.4×8 = 7.2$
$4x - 3.2 = 7.2$
$4x = 7.2 + 3.2$
$4x = 10.4$
$x = 2.6$
$(2x + 3)÷6 = 5$
$2x + 3 = 5×6$
$2x + 3 = 30$
$2x = 27$
$x = 13.5$
3. 看图列方程,并求出方程的解。
(1)

(2)

(1)
(2)
答案:
3.
(1)15.9+2x=17.5 x=0.8
(2)x+3x=480 x=120
(1)15.9+2x=17.5 x=0.8
(2)x+3x=480 x=120
4. 用方程表示下面的等量关系,并求出方程的解。
(1)$x$的$1.6$倍加上$9$的和是$33$。
(2)$x$减去$5$的差的$2$倍是$16.8$。
(1)$x$的$1.6$倍加上$9$的和是$33$。
(2)$x$减去$5$的差的$2$倍是$16.8$。
答案:
4.
(1)1.6x+9=33 x=15
(2)2(x-5)=16.8 x=13.4
(1)1.6x+9=33 x=15
(2)2(x-5)=16.8 x=13.4
5. 若$2.5×[16.5 - (□÷3 + 1.6)] = 20$,则$□$里的数是
20.7
。
答案:
5.20.7
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