Question

7/12+9/20-11/30+13/42-15/56简便运算

Answer 1

7/12+9/20-11/30+13/42-15/56
=7/12+1/4+1/5-（1/5+1/6）+1/6+1/7-（1/7+1/8）
=7/12+1/4+1/5-1/5-1/6+1/6+1/7-1/7-1/8
=7/12+（1/4-1/8）+（1/5-1/5）+（1/6-1/6）+（1/7-1/7）
=7/12+1/8
=17/24

Answer 2

7/12+9/20-11/30+13/42-15/56
=（1/3+1/4）+（1/4+1/5）-（1/5+1/6）+（1/6+1/7）-（1/7+1/8）
=1/3+1/4+1/4+1/5-1/5-1/6+1/6+1/7-1/7-1/8
=1/3+1/4+1/4-1/8
=1/3+3/8
=17/24
人合教育银城校区

Answer 3

7/12+9/20-11/30+13/42-15/56
=7/(3x4)+9/(4x5)-11/(5x6)+13/(6x7)-15/(7x8)
=7(1/3 -1/4)+9(1/4-1/5) - 11(1/5-1/6) + 13(1/6-1/7)-15(1/7-1/8)
=7(1/3) + (9-7)(1/4)-(9+11)(1/5)+(11+13)(1/6)-(13+15)(1/7) +15(1/8)
=7/3 + 2/4 - 4 + 4 - 4 +15/8
= 7/3 + 1/2 -4 +15/8
=1/3+1/2 -1/8
=1/3 + 3/8
=17/24

Answer 4

看后面的解答

追答

Answer 5

登鹳雀楼(王之涣)