How many onions should I cut
1 large onion equals 8 small ones
September 1, 2019, 
Often we can't imagine how many small onions we should cut instead of the big one.
Luckily, we can calculate this using a simple threedimensional sphere volume formula.
Suppose we have a large onion that has each of 3 dimensions twice the size of the small one.
If the radius r is, for example, 2 cm, then the radius of the large onion 2r is 4 cm.
The volume of a large sphere is always 8 times greater than the volume of a sphere with a half radius r.
V _{1} = 4 / 3 ˣ π ˣ (2r)^{3}
V_{2} = 4 / 3 ˣ π ˣ r^{3}
V _{1} = 4 / 3 ˣ 3,14 ˣ (4 cm)^{3}
V_{2} = 4 / 3 ˣ 3,14 ˣ (2 cm)^{3}
V _{1} = 4,19 ˣ 64 cm^{3}
V_{2} = 4,19 ˣ 8 cm^{3}
V_{1}: Volume of sphere / large onion
V_{2}: Volume of sphere / small onion
r_{1}: 2r  Radius of a large onion
r_{2}: r  Radius of a small onion
π: 3,14  Ludolf's number
V_{1} = 4 / 3 ˣ 3,14 ˣ 2r ˣ 2r ˣ 2r
V_{2} = 4 / 3 ˣ 3,14 ˣ r ˣ r ˣ r
V_{1} = 4,19 ˣ 8r^{3}
V_{2} = 4,19 ˣ r^{3}
V_{1} = 8 ˣ V_{2}
