6. A tank can hold 50 litres of water. At present, it is only 30% full. How many litres of water shall I put in the tank so that it is 50% full?​

30% of the total capacity will be=> 50*30/100 = 15 litres. we are required to fill it upto to 50%. So, 50% of the total capacity of the tank is=> 50*50/100 = 25 litres. therefore, amount of water to be put in the tank to get filled its desired amount is 25-15 = 10 liters.

10 litres

Step-by-step explanation:

50 litres - 100%

x litres - 30%

x=(50*30)/100=15 litres - that's 30% of the tank (this amount of water is already added)

50 litres - 100%

x litres - 50%

x=(50*50)/100=25 litres - that's 50% of the tank (this amount of water will be in the tank)

To find what amount of water should be added we must subtract the amount of water that is already added from the amount of water that will be in the tank.

25 - 15=10 litres should be added

i think it would be 42cm