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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)
89
×
91
(2)
2
33
(3)
2
38
(4)
81
×
79
(5)
92
×
88
(6)
21
×
19
(7)
62
×
58
(8)
92
×
88
(9)
69
×
71
(10)
2
29
(11)
2
43
(12)
2
41
©2026 数学クラブ http://sugaku.club/
月 日( )
【解答例】
(1)
89
×
91
2
2
=
(
90
−
1
)
(
90
+
1
)
=
90
−
1
=
8100
−
1
=
8099
(2)
2
33
2
2
2
=
(
30
+
3
)
=
30
+
2
×
30
×
3
+
3
=
900
+
180
+
9
=
1089
(3)
2
38
2
2
2
=
(
40
−
2
)
=
40
−
2
×
40
×
2
+
2
=
1600
−
160
+
4
=
1444
(4)
81
×
79
2
2
=
(
80
+
1
)
(
80
−
1
)
=
80
−
1
=
6400
−
1
=
6399
(5)
92
×
88
2
2
=
(
90
+
2
)
(
90
−
2
)
=
90
−
2
=
8100
−
4
=
8096
(6)
21
×
19
2
2
=
(
20
+
1
)
(
20
−
1
)
=
20
−
1
=
400
−
1
=
399
(7)
62
×
58
2
2
=
(
60
+
2
)
(
60
−
2
)
=
60
−
2
=
3600
−
4
=
3596
(8)
92
×
88
2
2
=
(
90
+
2
)
(
90
−
2
)
=
90
−
2
=
8100
−
4
=
8096
(9)
69
×
71
2
2
=
(
70
−
1
)
(
70
+
1
)
=
70
−
1
=
4900
−
1
=
4899
(10)
2
29
2
2
2
=
(
30
−
1
)
=
30
−
2
×
30
×
1
+
1
=
900
−
60
+
1
=
841
(11)
2
43
2
2
2
=
(
40
+
3
)
=
40
+
2
×
40
×
3
+
3
=
1600
+
240
+
9
=
1849
(12)
2
41
2
2
2
=
(
40
+
1
)
=
40
+
2
×
40
×
1
+
1
=
1600
+
80
+
1
=
1681