题目内容

计算
(1)(3
4
7
-3
4
7
×
2
5
)×0.7×
1
6

(2)7.816×1.45+1.69×7.816+3.14×2.184
(3)
2
15
×4.69+3.21×10
2
5
+7.9÷1
2
13

(4)(1+
7
11
)+(2+
7
11
×2)+(3+
7
11
×3)+…+(11+
7
11
×11)
(1)(3
4
7
-3
4
7
×
2
5
)×0.7×
1
6

=3
4
7
×(1-
2
5
)×0.7×
1
6

=
25
7
×
3
5
×0.7×
1
6

=0.25;

(2)7.816×1.45+1.69×7.816+3.14×2.184,
=7.816×(1.45+1.69)+3.14×2.184,
=7.816×3.14+3.14×2.184,
=3.14×(7.186+2.184),
=3.14×9.37,
=3.14×(10-0.63),
=31.4-1.9782,
=29.4218;

(3)
2
15
×4.69+3.21×10
2
5
+7.9÷1
2
13

=
1
15
×2×4.69+3.21×156×
1
15
+7.9×13×
1
15
),
=
1
15
×[2×4.69+3.21×156+7.9×13],
=
1
15
×[(2×7.9+150×3.21+7.9×13),
=
1
15
×(15×7.9+150×3.21),
=7.9+32.1,
=40;

(4)(1+
7
11
)+(2+
7
11
×2)+(3+
7
11
×3)+…+(11+
7
11
×11),
=(1+2+3+…+11)+(
7
11
+
7
11
×2+
7
11
×3+…+
7
11
×11),
=(1+11)×11÷2+
7
11
×(1+11)×11÷2,
=66+
7
11
×66,
=66+42,
=108.
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