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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)
79
×
81
(2)
82
×
78
(3)
2
58
(4)
18
×
22
(5)
2
72
(6)
2
83
(7)
2
68
(8)
2
51
(9)
2
31
(10)
2
81
(11)
37
×
43
(12)
77
×
83
©2026 数学クラブ http://sugaku.club/
月 日( )
【解答例】
(1)
79
×
81
2
2
=
(
80
−
1
)
(
80
+
1
)
=
80
−
1
=
6400
−
1
=
6399
(2)
82
×
78
2
2
=
(
80
+
2
)
(
80
−
2
)
=
80
−
2
=
6400
−
4
=
6396
(3)
2
58
2
2
2
=
(
60
−
2
)
=
60
−
2
×
60
×
2
+
2
=
3600
−
240
+
4
=
3364
(4)
18
×
22
2
2
=
(
20
−
2
)
(
20
+
2
)
=
20
−
2
=
400
−
4
=
396
(5)
2
72
2
2
2
=
(
70
+
2
)
=
70
+
2
×
70
×
2
+
2
=
4900
+
280
+
4
=
5184
(6)
2
83
2
2
2
=
(
80
+
3
)
=
80
+
2
×
80
×
3
+
3
=
6400
+
480
+
9
=
6889
(7)
2
68
2
2
2
=
(
70
−
2
)
=
70
−
2
×
70
×
2
+
2
=
4900
−
280
+
4
=
4624
(8)
2
51
2
2
2
=
(
50
+
1
)
=
50
+
2
×
50
×
1
+
1
=
2500
+
100
+
1
=
2601
(9)
2
31
2
2
2
=
(
30
+
1
)
=
30
+
2
×
30
×
1
+
1
=
900
+
60
+
1
=
961
(10)
2
81
2
2
2
=
(
80
+
1
)
=
80
+
2
×
80
×
1
+
1
=
6400
+
160
+
1
=
6561
(11)
37
×
43
2
2
=
(
40
−
3
)
(
40
+
3
)
=
40
−
3
=
1600
−
9
=
1591
(12)
77
×
83
2
2
=
(
80
−
3
)
(
80
+
3
)
=
80
−
3
=
6400
−
9
=
6391