数学题,帮帮忙~~~~~
简算(必须用简便方法)
(1)19*(98/99)=?
(2)(67+2/7)*(7/9)=?
参考答案:简算(必须用简便方法)
(1)19*(98/99)
=19*[1-1/99]
=19-19/99
=18+[1-19/99]
=18+80/99
=18又80/99
(2)(67+2/7)*(7/9)=?
=67*7/9+2/7*7/9
=[63+4]*7/9+2/9
=63*7/9+4*7/9+2/9
=49+28/9+2/9
=49+30/9
=49+3+1/3
=52又1/3