+
+
)×2419.9+19.9×99
3
÷
+3
÷
0.625×5.8+
×3.2+
.解:(1)(
+
+
)×24,=
×24+
×24+
×24,=12+8+4,
=24;
(2)19.9+19.9×99,
=19.9×(99+1),
=19.9×100,
=1990;
(3)3
÷
+3
÷
,=
×
+
×
=4
+10
,=15
;(4)0.625×5.8+
×3.2+
,=0.625×(5.8+3.2+1),
=0.625×10,
=6.25.
分析:(1)根据乘法分配律可得
×24+
×24+
×24,再计算即可求解;(2)根据乘法分配律可得19.9×(99+1),再计算即可求解;
(3)先算除法,再算加法;
(4)根据乘法分配律可得0.625×(5.8+3.2+1),再计算即可求解.
点评:考查了分数的简便计算,运算定律与简便运算,灵活运用运算律可以简化计算.