a.) 1/4
as shown on the picture.
b.) 216 liters.
So, first of all, you should know that if the tank was filled 10/10 of the full tank, it would be 240 liters. So, 10/10 of 240 is 240. Now, we calculate 1/10 of 240 which is 24 liters. Now multiply by 9 to find that 9/10 of the petrol tank is 216 liters.
Another shortcut is to multiply 240 by 9/10.
