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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)
31
×
29
(2)
88
×
92
(3)
31
×
29
(4)
91
×
89
(5)
53
×
47
(6)
2
38
(7)
61
×
59
(8)
2
62
(9)
2
71
(10)
2
73
(11)
2
63
(12)
2
53
©2026 数学クラブ http://sugaku.club/
月 日（ ）
【解答例】
(1)
31
×
29
2
2
=
(
30
＋
1
)
(
30
−
1
)
=
30
−
1
=
900
−
1
=
899
(2)
88
×
92
2
2
=
(
90
−
2
)
(
90
＋
2
)
=
90
−
2
=
8100
−
4
=
8096
(3)
31
×
29
2
2
=
(
30
＋
1
)
(
30
−
1
)
=
30
−
1
=
900
−
1
=
899
(4)
91
×
89
2
2
=
(
90
＋
1
)
(
90
−
1
)
=
90
−
1
=
8100
−
1
=
8099
(5)
53
×
47
2
2
=
(
50
＋
3
)
(
50
−
3
)
=
50
−
3
=
2500
−
9
=
2491
(6)
2
38
2
2
2
=
(
40
−
2
)
=
40
−
2
×
40
×
2
＋
2
=
1600
−
160
＋
4
=
1444
(7)
61
×
59
2
2
=
(
60
＋
1
)
(
60
−
1
)
=
60
−
1
=
3600
−
1
=
3599
(8)
2
62
2
2
2
=
(
60
＋
2
)
=
60
＋
2
×
60
×
2
＋
2
=
3600
＋
240
＋
4
=
3844
(9)
2
71
2
2
2
=
(
70
＋
1
)
=
70
＋
2
×
70
×
1
＋
1
=
4900
＋
140
＋
1
=
5041
(10)
2
73
2
2
2
=
(
70
＋
3
)
=
70
＋
2
×
70
×
3
＋
3
=
4900
＋
420
＋
9
=
5329
(11)
2
63
2
2
2
=
(
60
＋
3
)
=
60
＋
2
×
60
×
3
＋
3
=
3600
＋
360
＋
9
=
3969
(12)
2
53
2
2
2
=
(
50
＋
3
)
=
50
＋
2
×
50
×
3
＋
3
=
2500
＋
300
＋
9
=
2809