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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)
38
×
42
(2)
61
×
59
(3)
49
×
51
(4)
2
23
(5)
2
38
(6)
2
59
(7)
33
×
27
(8)
2
57
(9)
2
53
(10)
2
41
(11)
23
×
17
(12)
41
×
39
©2026 数学クラブ http://sugaku.club/
月 日（ ）
【解答例】
(1)
38
×
42
2
2
=
(
40
−
2
)
(
40
＋
2
)
=
40
−
2
=
1600
−
4
=
1596
(2)
61
×
59
2
2
=
(
60
＋
1
)
(
60
−
1
)
=
60
−
1
=
3600
−
1
=
3599
(3)
49
×
51
2
2
=
(
50
−
1
)
(
50
＋
1
)
=
50
−
1
=
2500
−
1
=
2499
(4)
2
23
2
2
2
=
(
20
＋
3
)
=
20
＋
2
×
20
×
3
＋
3
=
400
＋
120
＋
9
=
529
(5)
2
38
2
2
2
=
(
40
−
2
)
=
40
−
2
×
40
×
2
＋
2
=
1600
−
160
＋
4
=
1444
(6)
2
59
2
2
2
=
(
60
−
1
)
=
60
−
2
×
60
×
1
＋
1
=
3600
−
120
＋
1
=
3481
(7)
33
×
27
2
2
=
(
30
＋
3
)
(
30
−
3
)
=
30
−
3
=
900
−
9
=
891
(8)
2
57
2
2
2
=
(
60
−
3
)
=
60
−
2
×
60
×
3
＋
3
=
3600
−
360
＋
9
=
3249
(9)
2
53
2
2
2
=
(
50
＋
3
)
=
50
＋
2
×
50
×
3
＋
3
=
2500
＋
300
＋
9
=
2809
(10)
2
41
2
2
2
=
(
40
＋
1
)
=
40
＋
2
×
40
×
1
＋
1
=
1600
＋
80
＋
1
=
1681
(11)
23
×
17
2
2
=
(
20
＋
3
)
(
20
−
3
)
=
20
−
3
=
400
−
9
=
391
(12)
41
×
39
2
2
=
(
40
＋
1
)
(
40
−
1
)
=
40
−
1
=
1600
−
1
=
1599