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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
21
(3)
2
83
(4)
2
81
(5)
21
×
19
(6)
2
27
(7)
2
47
(8)
31
×
29
(9)
2
68
(10)
48
×
52
(11)
103
×
97
(12)
67
×
73
©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
21
2
2
2
=
(
20
＋
1
)
=
20
＋
2
×
20
×
1
＋
1
=
400
＋
40
＋
1
=
441
(3)
2
83
2
2
2
=
(
80
＋
3
)
=
80
＋
2
×
80
×
3
＋
3
=
6400
＋
480
＋
9
=
6889
(4)
2
81
2
2
2
=
(
80
＋
1
)
=
80
＋
2
×
80
×
1
＋
1
=
6400
＋
160
＋
1
=
6561
(5)
21
×
19
2
2
=
(
20
＋
1
)
(
20
−
1
)
=
20
−
1
=
400
−
1
=
399
(6)
2
27
2
2
2
=
(
30
−
3
)
=
30
−
2
×
30
×
3
＋
3
=
900
−
180
＋
9
=
729
(7)
2
47
2
2
2
=
(
50
−
3
)
=
50
−
2
×
50
×
3
＋
3
=
2500
−
300
＋
9
=
2209
(8)
31
×
29
2
2
=
(
30
＋
1
)
(
30
−
1
)
=
30
−
1
=
900
−
1
=
899
(9)
2
68
2
2
2
=
(
70
−
2
)
=
70
−
2
×
70
×
2
＋
2
=
4900
−
280
＋
4
=
4624
(10)
48
×
52
2
2
=
(
50
−
2
)
(
50
＋
2
)
=
50
−
2
=
2500
−
4
=
2496
(11)
103
×
97
2
2
=
(
100
＋
3
)
(
100
−
3
)
=
100
−
3
=
10000
−
9
=
9991
(12)
67
×
73
2
2
=
(
70
−
3
)
(
70
＋
3
)
=
70
−
3
=
4900
−
9
=
4891