\(A=\frac{10}{56}+\frac{10}{140}+\frac{10}{260}+..+\frac{10}{1400}\)
\(A=\frac{5}{28}+\frac{5}{70}+\frac{5}{130}+..+\frac{5}{700}\)
\(A.\frac{3}{5}=\frac{3}{4.7}+\frac{3}{7.10}+\frac{3}{10.13}+..+\frac{3}{25.28}\)
\(A.\frac{3}{5}=\frac{7-4}{4.7}+\frac{10-7}{7.10}+\frac{10-13}{10.13}+..+\frac{28-15}{25.28}\)
\(A.\frac{3}{5}=\frac{7}{4.7}-\frac{4}{4.7}+\frac{10}{7.10}-\frac{7}{7.10}+\frac{13}{13.10}+...+\frac{25}{25.28}-\frac{28}{25.28}\)
\(A.\frac{3}{5}=\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+\frac{1}{10}+...+\frac{1}{25}-\frac{1}{28}\)
\(A.\frac{3}{5}=\frac{1}{4}-\frac{1}{28}=\frac{6}{28}=\frac{3}{14}\)
\(A=\frac{3}{14}:\frac{3}{5}=\frac{5}{14}\)
A=
56
10
+
140
10
+
260
10
+..+
1400
10
�
=
5
28
+
5
70
+
5
130
+
.
.
+
5
700
A=
28
5
+
70
5
+
130
5
+..+
700
5
�
.
3
5
=
3
4.7
+
3
7.10
+
3
10.13
+
.
.
+
3
25.28
A.
5
3
=
4.7
3
+
7.10
3
+
10.13
3
+..+
25.28
3
�
.
3
5
=
7
−
4
4.7
+
10
−
7
7.10
+
10
−
13
10.13
+
.
.
+
28
−
15
25.28
A.
5
3
=
4.7
7−4
+
7.10
10−7
+
10.13
10−13
+..+
25.28
28−15
�
.
3
5
=
7
4.7
−
4
4.7
+
10
7.10
−
7
7.10
+
13
13.10
+
.
.
.
+
25
25.28
−
28
25.28
A.
5
3
=
4.7
7
−
4.7
4
+
7.10
10
−
7.10
7
+
13.10
13
+...+
25.28
25
−
25.28
28
�
.
3
5
=
1
4
−
1
7
+
1
7
−
1
10
+
1
10
+
.
.
.
+
1
25
−
1
28
A.
5
3
=
4
1
−
7
1
+
7
1
−
10
1
+
10
1
+...+
25
1
−
28
1
�
.
3
5
=
1
4
−
1
28
=
6
28
=
3
14
A.
5
3
=
4
1
−
28
1
=
28
6
=
14
3
�
=
3
14
:
3
5
=
5
14
A=
14
3
:
5
3
=
14
5
