Question

1*4*7 4*7*10 7*10*13.94*97*100

Answer 1

1(1×4)+1/(4×7)+1/(7×10)+1/(10×13)+……+1/(94×97)+1/(97×100)

=(1/3)×[3/(1×4)+3/(4×7)+3/(7×10)+3/(10×13)+……+3/(94×97)+3/(97×100)]

=(1/3)×(1-1/4+1/4-1/7+1/7-1/10+1/10-1/13+……+1/94-1/97+1/97-1/100)

=(1/3)×(1-1/100)

=1/3×99/100

=33/100