平均数是12.7的五个数排成一列，前三个数的平均数是12.8，后三个数的平均数是12.4，那么第三个数是多少？
直接写出得数+=×= 1﹣20%﹣= 4×==+25%= 3﹣==
直接写得数．= 4﹣1.63======== 27×5%=%==
直接写得数+=﹣=×=×=×÷×=+=×0+3= 3+1.75=÷=（+）×=
直接写得数．+0.625= 24×=÷9= （+）×12= 12×25%=÷=
直接写出得数== 3.14×8== 1﹣40%=== 52=
+
=
×
= 1﹣20%﹣
= 4×
=
=
+25%= 3﹣
=
=
= 4﹣1.63=
=
=
=
=
=
=
= 27×5%=
%=
=
+
=
﹣
=
×
=
×
=
×
÷
=
=
×0+3= 3
+1.75=
÷
=（
+
）×
=
+0.625= 24×
=
÷9=
+
）×12= 12×25%=
÷
=
=
= 3.14×8=
=
=
= 52=
粤公网安备 44130202000953号