Calculation: 1 / 1 × 4 + 1 / 4 × 7 + 1 / 7 × 10 + 1 / 10 × 13 + 1 / 13 × 16 + 1 / 16 × 19 + 1 / 19 × 22 =?

Calculation: 1 / 1 × 4 + 1 / 4 × 7 + 1 / 7 × 10 + 1 / 10 × 13 + 1 / 13 × 16 + 1 / 16 × 19 + 1 / 19 × 22 =?

1/1×4+1/4×7+1/7×10+1/10×13+1/13×16+1/16×19+1/19×22
=1/3(1-1/4+1/4-1/7+1/7-1/10+1/10-1/13+1/13-1/16+1/16-1/19+1/19-1/22)
=1/3(1-1/22)
=1/3 *(21/22)
=7/22