1+1/3+1/6+1/10+1/15+1/21+1/28求答案

　　 等于7/4

1+1/3(1+1/2)+1/5(1/2+1/3)+1/7(1/3+1/4)
=1+1/3*3/2+1/5*5/6+1/7*7/12
=1+1/2+1/6+1/12
=(1+1/2)+1/6(1+1/2)
=(1+1/6)(1+1/2)
=7/6*3/2
=7/4

1.75
或
7/4

原式=1+1/(1×3)+1/(2×3)+1/(2×5)+1/(3×5)+1/(3×7)+1/(4×7)
=1+[1/(1×3)+1/(2×3)]+[1/(2×5)+1/(3×5)]+[1/(3×7)+1/(4×7)]
=1+1+1/6+1/12
=2+1/4
=2.25

1+1／3+1／6+1／10+1／15+1／21+1／28
=1+2*(1/6+1/12+1/20+1/30+1/42+1/56)
=1+2*(1/2*3+1/3*4+1/4*5+1/5*6+1/6*7+1/7*8)
=1+2*(1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8)
=1+2*(1/2-1/8)
=1+2*3/8
=1+3/4=7/4