To find out how much fuel conditioner is needed for 54 L of fuel, we can set up a proportion using the given information.
Let x be the amount of fuel conditioner needed for 54 L of fuel.
According to the given information, the ratio of fuel conditioner to fuel is 90 ml / 20 L.
Therefore, we can set up the proportion:
90 ml / 20 L = x ml / 54 L
To solve for x, we can cross multiply and solve for x:
90 ml * 54 L = 20 L * x ml
4860 ml*L = 20L * x ml
4860 ml*L / 20 L = x ml
243 ml = x
Therefore, 243 ml of fuel conditioner is needed for 54 L of fuel.