You take the wt and divide by 2.2 to get kilos. Then take kilos and multiply by the ml to get the mg.
Take the desired mg divided by volume (160mg) multipy by the ml to get what dosage to give.
54lbs divided by 2.2 = 25 kilos
25 kilos x 5ml = 125mg
125mg over 160mg x 5ml = 600 over 160 divided 160 into 600 = 3.9 ml of medicine (tylenol)