This would depend on what type of oil you will be using for your premix. The oil base stock is either petroleum, semi-synthetic or synthetic oil and is mixed with gas at a ratio ranging from 16:1 (petroleum) to as high as 100:1 (synthetic). I personally ride a 2001 Kawasaki KDX200 that I run Yamalube 2R at 36:1 with no problems. Although synthetics say you can mix them at 100:1 I would not, that seems way too lean to me.
The 1984 model, 200 hp Yamaha requires a 50:1 ratio.
200 divided in the ratio of 19 = 10.526315789473685
It is A/200.
It is 200:1.
0.4 gallons
200
We need 200 tens to make 2000. 2000/10 = 200 So, there are 200 tens in 2000.
200+2000+20200
2000-200 = 1800
We need 200 tens to make 2000. 2000/10 = 200 So, there are 200 tens in 2000.
200:10 = 20:1
.5% = .5/100 = 1/200 so the ratio would be 1:200