a lorry tank was 3/5 full of petrol , 21 liters was added and it is now 5/6 full. how many liters of petrol can the tank hold
90litres
To find out how many liters of petrol the lorry tank can hold, we need to determine the capacity of the tank.
Let's assume the capacity of the tank is "C" liters.
We are given that the tank was initially 3/5 full, which means it contained 3/5 of its capacity. So, the initial amount of petrol in the tank was (3/5)C liters.
21 liters of petrol was added to the tank, bringing its level to 5/6 full. This means the tank now contains 5/6 of its capacity. So, the current amount of petrol in the tank is (5/6)C liters.
To determine the capacity of the tank, we can set up the following equation:
(3/5)C + 21 = (5/6)C
To solve for C, we can start by multiplying both sides of the equation by the least common multiple (LCM) of 5 and 6, which is 30:
30 * (3/5)C + 30 * 21 = 30 * (5/6)C
Simplifying, we get:
18C + 630 = 25C
Rearranging the equation, we have:
25C - 18C = 630
7C = 630
Dividing both sides by 7, we find:
C = 630 / 7
C = 90
Therefore, the lorry tank can hold 90 liters of petrol.
25/30 - 18/30 = 7/30
7/30 v = 21 L