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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
61
(3)
68
×
72
(4)
62
×
58
(5)
2
72
(6)
2
51
(7)
83
×
77
(8)
2
32
(9)
2
37
(10)
2
67
(11)
69
×
71
(12)
29
×
31
©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
61
2
2
2
=
(
60
＋
1
)
=
60
＋
2
×
60
×
1
＋
1
=
3600
＋
120
＋
1
=
3721
(3)
68
×
72
2
2
=
(
70
−
2
)
(
70
＋
2
)
=
70
−
2
=
4900
−
4
=
4896
(4)
62
×
58
2
2
=
(
60
＋
2
)
(
60
−
2
)
=
60
−
2
=
3600
−
4
=
3596
(5)
2
72
2
2
2
=
(
70
＋
2
)
=
70
＋
2
×
70
×
2
＋
2
=
4900
＋
280
＋
4
=
5184
(6)
2
51
2
2
2
=
(
50
＋
1
)
=
50
＋
2
×
50
×
1
＋
1
=
2500
＋
100
＋
1
=
2601
(7)
83
×
77
2
2
=
(
80
＋
3
)
(
80
−
3
)
=
80
−
3
=
6400
−
9
=
6391
(8)
2
32
2
2
2
=
(
30
＋
2
)
=
30
＋
2
×
30
×
2
＋
2
=
900
＋
120
＋
4
=
1024
(9)
2
37
2
2
2
=
(
40
−
3
)
=
40
−
2
×
40
×
3
＋
3
=
1600
−
240
＋
9
=
1369
(10)
2
67
2
2
2
=
(
70
−
3
)
=
70
−
2
×
70
×
3
＋
3
=
4900
−
420
＋
9
=
4489
(11)
69
×
71
2
2
=
(
70
−
1
)
(
70
＋
1
)
=
70
−
1
=
4900
−
1
=
4899
(12)
29
×
31
2
2
=
(
30
−
1
)
(
30
＋
1
)
=
30
−
1
=
900
−
1
=
899