简便计算下面各题:(1):14/15×8 (2):2/25×126 (3):35×11/36 (4)73×74/75 (5)1997/1998×19
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(1):14/15×8
=(1-1/15)×8……变一变,就简便
=8-8/15
=7又7/15
(2)2/25×126
= 2/25×(125+1)……变一变,就简便
=2/25×125+2/25×1
=10+2/25
=10又2/25
(3)35×11/36
=(36-1)×11/36
=36×11/36 -1×11/36
=11-11/36
=10又25/36
(4)73×74/75
=(75-2)×74/75
=75×74/75 -2×74/75
=74-1又73/75
=72又2/75
(5)1997/1998×19
=(1-1/1998)×19
=19-19/1998
=18又1979/1998
=(1-1/15)×8……变一变,就简便
=8-8/15
=7又7/15
(2)2/25×126
= 2/25×(125+1)……变一变,就简便
=2/25×125+2/25×1
=10+2/25
=10又2/25
(3)35×11/36
=(36-1)×11/36
=36×11/36 -1×11/36
=11-11/36
=10又25/36
(4)73×74/75
=(75-2)×74/75
=75×74/75 -2×74/75
=74-1又73/75
=72又2/75
(5)1997/1998×19
=(1-1/1998)×19
=19-19/1998
=18又1979/1998
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