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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)
78
×
82
(2)
67
×
73
(3)
2
39
(4)
2
83
(5)
89
×
91
(6)
2
73
(7)
23
×
17
(8)
2
71
(9)
71
×
69
(10)
21
×
19
(11)
2
61
(12)
61
×
59
©2026 数学クラブ http://sugaku.club/
月 日（ ）
【解答例】
(1)
78
×
82
2
2
=
(
80
−
2
)
(
80
＋
2
)
=
80
−
2
=
6400
−
4
=
6396
(2)
67
×
73
2
2
=
(
70
−
3
)
(
70
＋
3
)
=
70
−
3
=
4900
−
9
=
4891
(3)
2
39
2
2
2
=
(
40
−
1
)
=
40
−
2
×
40
×
1
＋
1
=
1600
−
80
＋
1
=
1521
(4)
2
83
2
2
2
=
(
80
＋
3
)
=
80
＋
2
×
80
×
3
＋
3
=
6400
＋
480
＋
9
=
6889
(5)
89
×
91
2
2
=
(
90
−
1
)
(
90
＋
1
)
=
90
−
1
=
8100
−
1
=
8099
(6)
2
73
2
2
2
=
(
70
＋
3
)
=
70
＋
2
×
70
×
3
＋
3
=
4900
＋
420
＋
9
=
5329
(7)
23
×
17
2
2
=
(
20
＋
3
)
(
20
−
3
)
=
20
−
3
=
400
−
9
=
391
(8)
2
71
2
2
2
=
(
70
＋
1
)
=
70
＋
2
×
70
×
1
＋
1
=
4900
＋
140
＋
1
=
5041
(9)
71
×
69
2
2
=
(
70
＋
1
)
(
70
−
1
)
=
70
−
1
=
4900
−
1
=
4899
(10)
21
×
19
2
2
=
(
20
＋
1
)
(
20
−
1
)
=
20
−
1
=
400
−
1
=
399
(11)
2
61
2
2
2
=
(
60
＋
1
)
=
60
＋
2
×
60
×
1
＋
1
=
3600
＋
120
＋
1
=
3721
(12)
61
×
59
2
2
=
(
60
＋
1
)
(
60
−
1
)
=
60
−
1
=
3600
−
1
=
3599