Question

5/1.4 + 5/4.7+...+5/97.100 = ?

Answer 1

 

A=5(1/1.4+1/4.7+1/7.10+...+1/97.100)

A:5.3=3/1.4+3/4.7+...+3/97.100

A.3/5=1-1/4+1/4+--1/7+...+1/94-1/97+1/97-1/100

A.3/5=1-1/100

A.3/5=99/100

A=99/100:3/5

A=33/20

Answer 2

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Answer 3

S¹=5/1×4 + 5/4×7 + ...+5/97×100

5/3× S¹=(1-1/4+1/4-1/7+...+1/97-1/100)

5/3× S¹=1-1/100

5/3× S¹= 99/100

S¹=99/100÷5/3

S¹=297/500