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©2026 数学クラブ http://sugaku.club/
月 日( )
● 次の計算をしなさい
[1C1-00]
(1)
2
82
(2)
102
×
98
(3)
2
67
(4)
81
×
79
(5)
17
×
23
(6)
47
×
53
(7)
2
72
(8)
2
43
(9)
2
79
(10)
2
21
(11)
31
×
29
(12)
78
×
82
©2026 数学クラブ http://sugaku.club/
月 日( )
【解答例】
(1)
2
82
2
2
2
=
(
80
+
2
)
=
80
+
2
×
80
×
2
+
2
=
6400
+
320
+
4
=
6724
(2)
102
×
98
2
2
=
(
100
+
2
)
(
100
−
2
)
=
100
−
2
=
10000
−
4
=
9996
(3)
2
67
2
2
2
=
(
70
−
3
)
=
70
−
2
×
70
×
3
+
3
=
4900
−
420
+
9
=
4489
(4)
81
×
79
2
2
=
(
80
+
1
)
(
80
−
1
)
=
80
−
1
=
6400
−
1
=
6399
(5)
17
×
23
2
2
=
(
20
−
3
)
(
20
+
3
)
=
20
−
3
=
400
−
9
=
391
(6)
47
×
53
2
2
=
(
50
−
3
)
(
50
+
3
)
=
50
−
3
=
2500
−
9
=
2491
(7)
2
72
2
2
2
=
(
70
+
2
)
=
70
+
2
×
70
×
2
+
2
=
4900
+
280
+
4
=
5184
(8)
2
43
2
2
2
=
(
40
+
3
)
=
40
+
2
×
40
×
3
+
3
=
1600
+
240
+
9
=
1849
(9)
2
79
2
2
2
=
(
80
−
1
)
=
80
−
2
×
80
×
1
+
1
=
6400
−
160
+
1
=
6241
(10)
2
21
2
2
2
=
(
20
+
1
)
=
20
+
2
×
20
×
1
+
1
=
400
+
40
+
1
=
441
(11)
31
×
29
2
2
=
(
30
+
1
)
(
30
−
1
)
=
30
−
1
=
900
−
1
=
899
(12)
78
×
82
2
2
=
(
80
−
2
)
(
80
+
2
)
=
80
−
2
=
6400
−
4
=
6396