Grade 10 — Mathematics 10-3 › T3U02 Imperial Measurement

Grade 10 › T3U02 Imperial Measurement › L2
GRADE 10 · ALBERTAOUTCOME MAT10-3-M2

L2 · American vs British imperial capacity (the gallon is not the gallon)

Learning goal

“I can explain how the American and British imperial systems split, state the litre value of both gallons, convert between litres and each gallon, and keep tons and tonnes straight.”

US gallon — the American capacity unit: 1 gal (US) ≈ 3.7854 L. The gallon in every US gas station and US recipe.
Imperial gallon — the British/Canadian-historical capacity unit: 1 gal (imp) ≈ 4.5461 L - about 20% bigger than the US gallon.
Bushel — a farm capacity unit for grain and produce; the US bushel ≈ 35.2391 L. (British bushels differed again - one more split.)
Ton vs tonne — a ton is imperial mass: 2000 lb. A tonne is SI mass: 1000 kg (≈ 2205 lb). Same sound, different amounts.
Worked example

Britain standardized its gallon in 1824 (the imperial gallon, based on 10 pounds of water). The young United States kept the OLDER, smaller gallon it had inherited - and the two systems have disagreed ever since. Canada used the imperial gallon until metrication in the 1970s, which is why older Canadian recipes, fuel economy figures and farm measures use the BIG gallon, while anything American uses the small one. The provided facts: 1 gal (US) ≈ 3.7854 L; 1 gal (imp) ≈ 4.5461 L; 1 gal (imp) ≈ 1.2 gal (US). Worked conversion: a 10 L jerry can in both systems. US: 10 / 3.7854 = 2.64 -> ≈ 2.64 gal (US). Imperial: 10 / 4.5461 = 2.20 -> ≈ 2.20 gal (imp). Same can, two counts - the bigger gallon gives the smaller count, every time. Reasonableness anchor: an imperial gallon is about 3/4 L more than a US gallon (4.5461 - 3.7854 ≈ 0.76 L).

Check yourself — explain it

The same 10 L can is 2.64 US gallons but only 2.20 imperial gallons because...

Paired problem — example still visible

Convert 20 L to imperial gallons -> 20 / 4.5461 = 4.399... -> ≈ 4.40 gal (imp)

Faded completion — last step is yours

"Convert 20 L to US gallons: 20 / 3.7854 = ___ gal (US) (nearest hundredth)." -> 5.28

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