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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)
79
×
81
(2)
2
22
(3)
43
×
37
(4)
81
×
79
(5)
41
×
39
(6)
59
×
61
(7)
79
×
81
(8)
97
×
103
(9)
2
53
(10)
2
37
(11)
2
48
(12)
52
×
48
©2026 数学クラブ http://sugaku.club/
月 日（ ）
【解答例】
(1)
79
×
81
2
2
=
(
80
−
1
)
(
80
＋
1
)
=
80
−
1
=
6400
−
1
=
6399
(2)
2
22
2
2
2
=
(
20
＋
2
)
=
20
＋
2
×
20
×
2
＋
2
=
400
＋
80
＋
4
=
484
(3)
43
×
37
2
2
=
(
40
＋
3
)
(
40
−
3
)
=
40
−
3
=
1600
−
9
=
1591
(4)
81
×
79
2
2
=
(
80
＋
1
)
(
80
−
1
)
=
80
−
1
=
6400
−
1
=
6399
(5)
41
×
39
2
2
=
(
40
＋
1
)
(
40
−
1
)
=
40
−
1
=
1600
−
1
=
1599
(6)
59
×
61
2
2
=
(
60
−
1
)
(
60
＋
1
)
=
60
−
1
=
3600
−
1
=
3599
(7)
79
×
81
2
2
=
(
80
−
1
)
(
80
＋
1
)
=
80
−
1
=
6400
−
1
=
6399
(8)
97
×
103
2
2
=
(
100
−
3
)
(
100
＋
3
)
=
100
−
3
=
10000
−
9
=
9991
(9)
2
53
2
2
2
=
(
50
＋
3
)
=
50
＋
2
×
50
×
3
＋
3
=
2500
＋
300
＋
9
=
2809
(10)
2
37
2
2
2
=
(
40
−
3
)
=
40
−
2
×
40
×
3
＋
3
=
1600
−
240
＋
9
=
1369
(11)
2
48
2
2
2
=
(
50
−
2
)
=
50
−
2
×
50
×
2
＋
2
=
2500
−
200
＋
4
=
2304
(12)
52
×
48
2
2
=
(
50
＋
2
)
(
50
−
2
)
=
50
−
2
=
2500
−
4
=
2496