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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)
42
×
38
(2)
79
×
81
(3)
2
67
(4)
21
×
19
(5)
2
33
(6)
2
38
(7)
61
×
59
(8)
2
47
(9)
2
22
(10)
39
×
41
(11)
2
29
(12)
2
28
©2025 数学クラブ http://sugaku.club/
月 日（ ）
【解答例】
(1)
42
×
38
2
2
=
(
40
＋
2
)
(
40
−
2
)
=
40
−
2
=
1600
−
4
=
1596
(2)
79
×
81
2
2
=
(
80
−
1
)
(
80
＋
1
)
=
80
−
1
=
6400
−
1
=
6399
(3)
2
67
2
2
2
=
(
70
−
3
)
=
70
−
2
×
70
×
3
＋
3
=
4900
−
420
＋
9
=
4489
(4)
21
×
19
2
2
=
(
20
＋
1
)
(
20
−
1
)
=
20
−
1
=
400
−
1
=
399
(5)
2
33
2
2
2
=
(
30
＋
3
)
=
30
＋
2
×
30
×
3
＋
3
=
900
＋
180
＋
9
=
1089
(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
47
2
2
2
=
(
50
−
3
)
=
50
−
2
×
50
×
3
＋
3
=
2500
−
300
＋
9
=
2209
(9)
2
22
2
2
2
=
(
20
＋
2
)
=
20
＋
2
×
20
×
2
＋
2
=
400
＋
80
＋
4
=
484
(10)
39
×
41
2
2
=
(
40
−
1
)
(
40
＋
1
)
=
40
−
1
=
1600
−
1
=
1599
(11)
2
29
2
2
2
=
(
30
−
1
)
=
30
−
2
×
30
×
1
＋
1
=
900
−
60
＋
1
=
841
(12)
2
28
2
2
2
=
(
30
−
2
)
=
30
−
2
×
30
×
2
＋
2
=
900
−
120
＋
4
=
784