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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)
91
×
89
(2)
2
27
(3)
2
77
(4)
2
72
(5)
21
×
19
(6)
2
81
(7)
2
72
(8)
57
×
63
(9)
2
27
(10)
2
37
(11)
2
39
(12)
2
49
©2026 数学クラブ http://sugaku.club/
月 日（ ）
【解答例】
(1)
91
×
89
2
2
=
(
90
＋
1
)
(
90
−
1
)
=
90
−
1
=
8100
−
1
=
8099
(2)
2
27
2
2
2
=
(
30
−
3
)
=
30
−
2
×
30
×
3
＋
3
=
900
−
180
＋
9
=
729
(3)
2
77
2
2
2
=
(
80
−
3
)
=
80
−
2
×
80
×
3
＋
3
=
6400
−
480
＋
9
=
5929
(4)
2
72
2
2
2
=
(
70
＋
2
)
=
70
＋
2
×
70
×
2
＋
2
=
4900
＋
280
＋
4
=
5184
(5)
21
×
19
2
2
=
(
20
＋
1
)
(
20
−
1
)
=
20
−
1
=
400
−
1
=
399
(6)
2
81
2
2
2
=
(
80
＋
1
)
=
80
＋
2
×
80
×
1
＋
1
=
6400
＋
160
＋
1
=
6561
(7)
2
72
2
2
2
=
(
70
＋
2
)
=
70
＋
2
×
70
×
2
＋
2
=
4900
＋
280
＋
4
=
5184
(8)
57
×
63
2
2
=
(
60
−
3
)
(
60
＋
3
)
=
60
−
3
=
3600
−
9
=
3591
(9)
2
27
2
2
2
=
(
30
−
3
)
=
30
−
2
×
30
×
3
＋
3
=
900
−
180
＋
9
=
729
(10)
2
37
2
2
2
=
(
40
−
3
)
=
40
−
2
×
40
×
3
＋
3
=
1600
−
240
＋
9
=
1369
(11)
2
39
2
2
2
=
(
40
−
1
)
=
40
−
2
×
40
×
1
＋
1
=
1600
−
80
＋
1
=
1521
(12)
2
49
2
2
2
=
(
50
−
1
)
=
50
−
2
×
50
×
1
＋
1
=
2500
−
100
＋
1
=
2401