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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)
71
×
69
(2)
28
×
32
(3)
2
21
(4)
28
×
32
(5)
2
32
(6)
92
×
88
(7)
2
28
(8)
67
×
73
(9)
27
×
33
(10)
2
61
(11)
57
×
63
(12)
91
×
89
©2026 数学クラブ http://sugaku.club/
月 日（ ）
【解答例】
(1)
71
×
69
2
2
=
(
70
＋
1
)
(
70
−
1
)
=
70
−
1
=
4900
−
1
=
4899
(2)
28
×
32
2
2
=
(
30
−
2
)
(
30
＋
2
)
=
30
−
2
=
900
−
4
=
896
(3)
2
21
2
2
2
=
(
20
＋
1
)
=
20
＋
2
×
20
×
1
＋
1
=
400
＋
40
＋
1
=
441
(4)
28
×
32
2
2
=
(
30
−
2
)
(
30
＋
2
)
=
30
−
2
=
900
−
4
=
896
(5)
2
32
2
2
2
=
(
30
＋
2
)
=
30
＋
2
×
30
×
2
＋
2
=
900
＋
120
＋
4
=
1024
(6)
92
×
88
2
2
=
(
90
＋
2
)
(
90
−
2
)
=
90
−
2
=
8100
−
4
=
8096
(7)
2
28
2
2
2
=
(
30
−
2
)
=
30
−
2
×
30
×
2
＋
2
=
900
−
120
＋
4
=
784
(8)
67
×
73
2
2
=
(
70
−
3
)
(
70
＋
3
)
=
70
−
3
=
4900
−
9
=
4891
(9)
27
×
33
2
2
=
(
30
−
3
)
(
30
＋
3
)
=
30
−
3
=
900
−
9
=
891
(10)
2
61
2
2
2
=
(
60
＋
1
)
=
60
＋
2
×
60
×
1
＋
1
=
3600
＋
120
＋
1
=
3721
(11)
57
×
63
2
2
=
(
60
−
3
)
(
60
＋
3
)
=
60
−
3
=
3600
−
9
=
3591
(12)
91
×
89
2
2
=
(
90
＋
1
)
(
90
−
1
)
=
90
−
1
=
8100
−
1
=
8099