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©2025 数学クラブ http://sugaku.club/
月 日（ ）
● 次の計算をしなさい
[1C1-00]
(1)
51
×
49
(2)
23
×
17
(3)
2
62
(4)
78
×
82
(5)
2
22
(6)
2
87
(7)
38
×
42
(8)
101
×
99
(9)
2
41
(10)
102
×
98
(11)
2
38
(12)
82
×
78
©2025 数学クラブ http://sugaku.club/
月 日（ ）
【解答例】
(1)
51
×
49
2
2
=
(
50
＋
1
)
(
50
−
1
)
=
50
−
1
=
2500
−
1
=
2499
(2)
23
×
17
2
2
=
(
20
＋
3
)
(
20
−
3
)
=
20
−
3
=
400
−
9
=
391
(3)
2
62
2
2
2
=
(
60
＋
2
)
=
60
＋
2
×
60
×
2
＋
2
=
3600
＋
240
＋
4
=
3844
(4)
78
×
82
2
2
=
(
80
−
2
)
(
80
＋
2
)
=
80
−
2
=
6400
−
4
=
6396
(5)
2
22
2
2
2
=
(
20
＋
2
)
=
20
＋
2
×
20
×
2
＋
2
=
400
＋
80
＋
4
=
484
(6)
2
87
2
2
2
=
(
90
−
3
)
=
90
−
2
×
90
×
3
＋
3
=
8100
−
540
＋
9
=
7569
(7)
38
×
42
2
2
=
(
40
−
2
)
(
40
＋
2
)
=
40
−
2
=
1600
−
4
=
1596
(8)
101
×
99
2
2
=
(
100
＋
1
)
(
100
−
1
)
=
100
−
1
=
10000
−
1
=
9999
(9)
2
41
2
2
2
=
(
40
＋
1
)
=
40
＋
2
×
40
×
1
＋
1
=
1600
＋
80
＋
1
=
1681
(10)
102
×
98
2
2
=
(
100
＋
2
)
(
100
−
2
)
=
100
−
2
=
10000
−
4
=
9996
(11)
2
38
2
2
2
=
(
40
−
2
)
=
40
−
2
×
40
×
2
＋
2
=
1600
−
160
＋
4
=
1444
(12)
82
×
78
2
2
=
(
80
＋
2
)
(
80
−
2
)
=
80
−
2
=
6400
−
4
=
6396