Simple calculation: 1 / 3 + 1 / 8 + 1 / 15 +. + 1 / 120

Simple calculation: 1 / 3 + 1 / 8 + 1 / 15 +. + 1 / 120

1/3+1/8+1/15+.+1/120
=(1/2)*(1-1/3+1/2-1/4+1/3-1/5+1/4-1/5+.+1/9-1/11+1/10-1/12)
=(1/2)*(1+1/2-1/11-1/12)
=(1/2)*175/132
=175/264

Simple calculation (3 / 4 ／ 1 / 4 + 15) ／ 120%

(3 / 4 ／ 1 / 4 + 15) ／ 120%
=（3＋15）÷120％
=18÷1.2
=180÷12
=15

1 and 1 / 8:1 and 1 / 4:1 1.6:2.4:4 1.5:1 / 2:3 1.2 hours: simplification

1 and 1 / 8:1 and 1 / 4:1 = 9 / 8:5 / 4:1 = (8 × 9 / 8): (8 × 5 / 4): (8 × 1) = 9:10:81.6:2.4:4 = 8 / 5:12 / 5:4 = (5 / 4 × 8 / 5): (5 / 4 × 12 / 5): (5 / 4 × 4) = 2:3:51.5:1 / 2:3 = (2 × 1.5): (2 × 1 / 2): (2 × 3) = 3:1:6120 minutes: 1.2 hours: 1 hour 20

Simple calculation 1 / 3 + 1 / 15 +. + 1 / 120

1 divided by 3 times (the nth power of 5), the denominator is an equal ratio sequence, and then a formula a (n + 1) / an = q (n ∈ n *)