我能很快算出下面的题目相信你也能行.
来源:学生作业帮 编辑:作业帮 分类:数学作业 时间:2024/07/18 03:32:57
①9
2 5 -(3 3 7 +0.4), =9 2 5 -3 3 7 - 2 5 , =(9 2 5 - 2 5 )-3 3 7 , =9-3 3 7 , =5 4 7 ; ②7.8× 1 5 +2.2×20%, =7.8×0.2+2.2×0.2, =(7.8+2.2)×0.2, =10×0.2, =2; ③34.7- 7 15 +65.3- 8 15 , =(34.7+65.3)-( 7 15 + 8 15 ), =100-1, =99; ④( 3 4 + 11 6 - 13 24 )×12, = 3 4 ×12+ 11 6 ×12- 13 24 ×12, =9+22-6.5, =24.5; ⑤0.25×32×12.5, =0.25×4×8×12.5, =(0.25×4)×(8×12.5), =1×100, =100; ⑥ 7 12 ×[ 3 4 -( 11 20 - 1 2 )], = 7 12 ×[ 3 4 -( 11 20 - 10 20 )], = 7 12 ×[ 3 4 - 1 20 ], = 7 12 ×[ 15 20 - 1 20 ], = 7 12 × 7 10 , = 49 120 ; ⑦ 1 3 x+ 5 9 x=1.4, ( 1 3 + 5 9 )x=1.4, 8 9 x=1.4, 8 9 x× 9 8 =1.4× 9 8 , x= 63 40 ; ⑧16:x=0.75: 15 8 , 0.75x=16× 15 8 , 0.75x=30, 0.75x÷0.75=30÷0.75, x=40. |