下面各题怎样算简便就怎样算. ①1.8×1/4+2.2×25% ②99×61.25+61.25 ③9/20÷〔1/2×(2/5+4/5)〕 ④45+99×99+54.

问题描述:

下面各题怎样算简便就怎样算.
①1.8×

1
4
+2.2×25%
②99×61.25+61.25
9
20
÷〔
1
2
×(
2
5
+
4
5
)〕
④45+99×99+54.

(1)1.8×

1
4
+2.2×25%,
=(1.8+2.2)×25%,
=4×25%,
=1;
(2)99×61.25+61.25,
=(99+1)×61.25,
=100×61.25,
=6125;
(3)
9
20
÷〔
1
2
×(
2
5
+
4
5
)〕,
=
9
20
÷〔
1
2
×
6
5
],
=
9
20
÷
3
5

=
3
4

(4)45+99×99+54,
=(45+54)+99×99,
=99+99×99,
=(99+1)×99,
=100×99,
=9900.