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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)
102
×
98
(2)
49
×
51
(3)
63
×
57
(4)
2
71
(5)
2
87
(6)
2
37
(7)
2
78
(8)
2
51
(9)
2
79
(10)
23
×
17
(11)
77
×
83
(12)
2
23
©2026 数学クラブ http://sugaku.club/
月 日( )
【解答例】
(1)
102
×
98
2
2
=
(
100
+
2
)
(
100
−
2
)
=
100
−
2
=
10000
−
4
=
9996
(2)
49
×
51
2
2
=
(
50
−
1
)
(
50
+
1
)
=
50
−
1
=
2500
−
1
=
2499
(3)
63
×
57
2
2
=
(
60
+
3
)
(
60
−
3
)
=
60
−
3
=
3600
−
9
=
3591
(4)
2
71
2
2
2
=
(
70
+
1
)
=
70
+
2
×
70
×
1
+
1
=
4900
+
140
+
1
=
5041
(5)
2
87
2
2
2
=
(
90
−
3
)
=
90
−
2
×
90
×
3
+
3
=
8100
−
540
+
9
=
7569
(6)
2
37
2
2
2
=
(
40
−
3
)
=
40
−
2
×
40
×
3
+
3
=
1600
−
240
+
9
=
1369
(7)
2
78
2
2
2
=
(
80
−
2
)
=
80
−
2
×
80
×
2
+
2
=
6400
−
320
+
4
=
6084
(8)
2
51
2
2
2
=
(
50
+
1
)
=
50
+
2
×
50
×
1
+
1
=
2500
+
100
+
1
=
2601
(9)
2
79
2
2
2
=
(
80
−
1
)
=
80
−
2
×
80
×
1
+
1
=
6400
−
160
+
1
=
6241
(10)
23
×
17
2
2
=
(
20
+
3
)
(
20
−
3
)
=
20
−
3
=
400
−
9
=
391
(11)
77
×
83
2
2
=
(
80
−
3
)
(
80
+
3
)
=
80
−
3
=
6400
−
9
=
6391
(12)
2
23
2
2
2
=
(
20
+
3
)
=
20
+
2
×
20
×
3
+
3
=
400
+
120
+
9
=
529