Question

How many liters of wine can be held in a wine barrel whose capacity is 33 gal?

Answer 1

These units always present a probem in conversions. Because a US Gallon is distinct from an Imperial Gallon. If you live in the States, you will use the US Gallon.
1 US Gallon = 3.785 L.
Thus, 33 gallons x 3.785 L x gallon−1 = 124.9 L ≈ 125 L
If you live in the United Kingdom, you will use the UK Gallon.
1 UK Gallon = 4.546 L.
Thus, 33 gallons x 4.546 L x gallon−1 = 150 L