这个题首先要找出三个最小公倍数,2 3 的公倍数有6 12 24…
2 4的公倍数有4 8 12 24…
3 4的公倍数有12 24…
这3个最小公倍数是12,分母就选择12
1/2*6=6/12
2/3*4=8/12
3/4*3=9/12
6/12+8/12+9/12=23/23=
1又11/12
1/2+2/3+3/4
=(1-1/2)+(1-1/3)+(1-1/4)
=3-(1/2+1/3+1/4)
=3-(6/12+4/12+3/12)
=3-(13/12)
=3-1-1/12
=2-1/12
=1+11/12
式中“+”读作“又”。
1/2+2/3+3/4
=(6+2*4+3*3)/12
=23/12
=1又11/12
1/2+2/3+3/4
=(1-1/2)+(1-1/3)+(1-1/4)
=3-(1/2+1/3+1/4)
=3-(6/12+4/12+3/12)
=3-(13/12)
=3-1-1/12
=2-1/12
=1又11/12