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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)
2
59
(2)
49
×
51
(3)
51
×
49
(4)
2
81
(5)
42
×
38
(6)
18
×
22
(7)
2
49
(8)
78
×
82
(9)
69
×
71
(10)
62
×
58
(11)
2
82
(12)
38
×
42
©2026 数学クラブ http://sugaku.club/
月 日（ ）
【解答例】
(1)
2
59
2
2
2
=
(
60
−
1
)
=
60
−
2
×
60
×
1
＋
1
=
3600
−
120
＋
1
=
3481
(2)
49
×
51
2
2
=
(
50
−
1
)
(
50
＋
1
)
=
50
−
1
=
2500
−
1
=
2499
(3)
51
×
49
2
2
=
(
50
＋
1
)
(
50
−
1
)
=
50
−
1
=
2500
−
1
=
2499
(4)
2
81
2
2
2
=
(
80
＋
1
)
=
80
＋
2
×
80
×
1
＋
1
=
6400
＋
160
＋
1
=
6561
(5)
42
×
38
2
2
=
(
40
＋
2
)
(
40
−
2
)
=
40
−
2
=
1600
−
4
=
1596
(6)
18
×
22
2
2
=
(
20
−
2
)
(
20
＋
2
)
=
20
−
2
=
400
−
4
=
396
(7)
2
49
2
2
2
=
(
50
−
1
)
=
50
−
2
×
50
×
1
＋
1
=
2500
−
100
＋
1
=
2401
(8)
78
×
82
2
2
=
(
80
−
2
)
(
80
＋
2
)
=
80
−
2
=
6400
−
4
=
6396
(9)
69
×
71
2
2
=
(
70
−
1
)
(
70
＋
1
)
=
70
−
1
=
4900
−
1
=
4899
(10)
62
×
58
2
2
=
(
60
＋
2
)
(
60
−
2
)
=
60
−
2
=
3600
−
4
=
3596
(11)
2
82
2
2
2
=
(
80
＋
2
)
=
80
＋
2
×
80
×
2
＋
2
=
6400
＋
320
＋
4
=
6724
(12)
38
×
42
2
2
=
(
40
−
2
)
(
40
＋
2
)
=
40
−
2
=
1600
−
4
=
1596