Question

Aryan is washing cars for a fundraiser. His buckets contain 25 liters 215 milliliters of water. He adds another 6 liters 55 milliliters of water to the buckets before getting started. If at the end of the first hour of washing, Aryan has 8 liters 740 milliliters of water remaining, how much water has he already
used?

Answer 1

25.215 + 6.055 - x = 8.740

Answer 2

The easy way to do this is to convert everything to the same unit; i.e., either to liters (L) or milliliters (mL). I prefer to convert to L. Remember that 1000 mL = 1L so just divide mL by 1000 to obtain L. Remember, too, dividing by 10 or 100 or 1000 you just move the decimal point to the left y1, or 2 or 3 places. So if I want to convert 125 mL to L that is 0.125 L. 15,000 mL = 15 L and so on. To the problem.
So the bucket contains 25 L and 215 mL. In L that is 25.215 L.
He adds another 6 L and 55 mL. in L that is 6.055 L. The total now is 25.215 + 6.055 = 31.270 L
At the end of the first hour he has 8 L and 740 mL = 8.740 L left.
He has used 31.270 - 8.740 = ? Liters