Question

1) A = 7/ 10.11 + 7/ 11.12 + 7/ 12.13 + .... + 7/69.70

2 ) B = 1/ 25.27 + 1/ 27.29 + 1/29.31+ ......+ 1/ 73.75

Answer 1

1) A=7/10.11+7/11.12+7/12.13+...+7/69.70

  A=7.(1/10.11+1/11.12+1/12.13+...+1/69.70)

 A= 7.(1/10-1/11+1/11-1/12+1/12-1/13+...+1/69-1/70)

 A= 7.(1/10-1/70)

 A=7.3/35=3/5

2)B=1/25.27+1/27.29+1/29.31+...+1/73.1/75

  B=1/25-1/27+1/27-1/29+1/29-1/31+...+1/73-1/75

  B=1/25-1/75=2/75

Answer 2

A = 7/ 10.11 + 7/ 11.12 + 7/ 12.13 + .... + 7/69.70

(1/7).A=1/10.11+1/11.12+...+1/69.70

=1/10-1/11+1/11-1/12+...+1/69-1/70

=1/10-1/70=3/35

=>A=7.(3/35)

=3/5

2 ) B = 1/ 25.27 + 1/ 27.29 + 1/29.31+ ......+ 1/ 73.75

=>(1/2).B=2/25.27+...+2.73.75

=1/25-1/27+...+1/73-1/75

=1/25-1/75

=2/75

=>B=4/75

Answer 3

 A=7.(1/10.11+1/11.12+1/12.13+...+1/69.70)

 A= 7.(1/10-1/11+1/11-1/12+1/12-1/13+...+1/69-1/70)

 A= 7.(1/10-1/70)

 A=7.3/35=3/5

2)B=1/25.27+1/27.29+1/29.31+...+1/73.1/75

  B=1/25-1/27+1/27-1/29+1/29-1/31+...+1/73-1/75

  B=1/25-1/75=2/75

Answer 4

A= 7(1/10.11+1/11.12+1/12.13+...+1/69.70)

A= 7.(1/10-1/11+1/11-1/12+1/12-1/13+...+1/69-1/70)

A= 7.(1/10-1/70)

A= 7. 3/35

A=3/5

2) B= 1/25.27+1/27.29+1/29.31+....1/73.75

B = 1/25-1/27+1/27-1/29+1/29-1/31+....+1/73-1/75

B= 1/25-1/75

B = 2/75

Answer 5

1) A = 7/10.11+7/11.12+7/12.13+...+7/69.70

      = 7.(1/10.11+1/11.12+1/12.13+...+1/69.70)

     =7.(1/10-1/11+1/11-1/12+....+1/69-1/70)

     =7.(1/10-1/70)

     =7.6/70

     =6/10=3/5