Question

数学 、 用简便方法计算..

1. （3/4+1/5+1/4+4/5）×1又2/5 2. （1/6+1/8+7/12）×2.4

3. （1/3+1/5）×3×5 4. 35/8×5/7+2/7÷8/35

5. 2001×1999/2000 6. 1999/2000×1999

7. 9/4-（2/7+5/4）-2/7 8. 4/5×0.25+13/5×1/4+3/5÷4

9. 7/9×2/13+11/9×7/13 10. 3/8×7+0.375

11. 1/1×3+ 1/3×5+ 1/5×7+ 1/7×9

12. 1/3×1/8+1/8×1/13+1/13×1/18

13. 1/4-1/8-1/16-1/32-1/64 14. 1/4+1/8+1/16+1/32+1/64

15. 1/6+1/12+1/20+1/30 16. 7/6+13/12+21/20+31/30
过程要写清楚点
才能加分
满意加两百分
真的急要滴

Answer 1

1. （3/4+1/5+1/4+4/5）×1又2/5
=(3/4+1/4+1/5+4/5)×7/5
=(1+1)*7/5
=14/5
2. （1/6+1/8+7/12）×2.4
=（1/6+1/8+7/12）×12/5
=2/5+3/10+7/5
=21/10
3. （1/3+1/5）×3×5
=1/3*3*5+1/5*5*3
=5+3
=8
4. 35/8×5/7+2/7÷8/35
=35/8×5/7+2/7*35/8
=35/8*(5/7+2/7)
=35/8
5. 2001×1999/2000
=(2000+1)*1999/2000
=1999+1999/2000
6. 1999/2000×1999
=1999/2000*(2000-1)
1999-1999/2000
7. 9/4-（2/7+5/4）-2/7
= 9/4-2/7-5/4-2/7
=9/4-5/4-2/7-2/7
=1-4/7
=3/7
8. 4/5×0.25+13/5×1/4+3/5÷4
=4/5×1/4+13/5×1/4+3/5*1/4
=(4/5+13/5+3/5)*1/4
=4*1/4
=1
9. 7/9×2/13+11/9×7/13
=14/117=77/117
=91/117
10. 3/8×7+0.375
=3/8(7+1)
=3
11. 1/1×3+ 1/3×5+ 1/5×7+ 1/7×9
=3+5/3+7/5+9/7
=3+225/105+147/105+135/105
=3+507/105
12. 1/3×1/8+1/8×1/13+1/13×1/18
=1/24+1/13(1/8+1/18)
=1/24+1/13*13/36
=1/24+1/36
=60/864
=5/72
13. 1/4-1/8-1/16-1/32-1/64
=16/64-8/64-4/64-2/64-1/64
=1/64
14. 1/4+1/8+1/16+1/32+1/64
=16/64+8/64+4/64+2/64+1/64
31/64
15. 1/6+1/12+1/20+1/30
=6/60+5/60+3/60+2/60
=16/60
=4/15
16. 7/6+13/12+21/20+31/30
=70/60+65/60+63/60+62/60
=260/60
=13/3

Answer 2

使用计算器算吧，再把小数化为分数，就行了

Answer 3

3,（1/3+1/5）×3×5
=1/3×3+1/5×5
=1+1
=2

Answer 4

a