Xuan purchased a bottle of oil. She used ⁵₉ of the oil in January. She then used the remaining oil in February and March in the ratio 1 : 9. Given that the amount of the oil used in March was 0.35 ℓ less than that in January, how many millilitres of oil did the bottle contain at first?

January	February	March	Total
5x5	4x5		9x5
	1x2	9x2
25 u	2 u	18 u	45 u

Total volume of February and March is combined repeated identity. Make the total volume of February and March the same. LCM of 4 and 10 is 20.

Volume of less oil syrup in the bottle used in March than January
= 25 u - 18 u
= 7 u

7 u = 0.35 

1 u = 0.35 ÷ 7 = 0.05

Amount of oil in the bottle at first
= 45 u
= 45 x 0.05
= 2.25 ℓ

1 ℓ = 1000 mℓ

Amount of oil in the bottle at first
= 2.25 x 1000
= 2250 mℓ

Answer(s): 2250 mℓ