A lorry tank was 4/5 full of petrol when the guage indicated 12 litres.what was the full capacity of the tank in litres

(4/5)x = 12

Solve for x

To find the full capacity of the tank in liters, we need to determine the capacity of the tank when it is 4/5 full.

If the tank is 4/5 full when the gauge indicates 12 liters, it means that 12 liters is equal to 4/5 of the tank's capacity.

We can set up a proportion to find the tank's capacity:

(12 liters) / (4/5) = (x liters) / 1

To solve the proportion, we can cross multiply:

12 liters * 1 = (4/5) * x liters

12 = (4/5) * x

To isolate x, we need to divide both sides of the equation by (4/5):

12 / (4/5) = x

To divide by a fraction, we can multiply by its reciprocal:

12 * (5/4) = x

Simplifying the expression on the right side:

60/4 = x

Now, divide 60 by 4:

x = 15

Therefore, the full capacity of the tank is 15 liters.