To find out how many litres of soup were used throughout the day, we can subtract the amount of soup left at the end of the day from the amount of soup at the start of the day:
Start of day: 6 1/2 litres
End of day: 2 1/10 litres
We need to convert both quantities to a common denominator before we can subtract them:
Start of day: 6 1/2 = 13/2
End of day: 2 1/10 = 21/10
Now we can subtract:
13/2 - 21/10
To do this, we need to find a common denominator, which is 10:
13/2 = 65/10
21/10 = 21/10
Now we can subtract:
65/10 - 21/10 = 44/10
So the soup kitchen used 44/10 litres of soup throughout the day, which simplifies to 4 2/5 litres. Therefore, they used 4 2/5 litres of soup throughout the day.