Marion purchased a bottle of detergent. She used ⁵₇ of the detergent in March. She then used the remaining detergent in April and May in the ratio 1 : 2. Given that the amount of the detergent used in May was 0.99 ℓ less than that in March, how many millilitres of detergent did the bottle contain at first?

March	April	May	Total
5x3	2x3		7x3
	1x2	2x2
15 u	2 u	4 u	21 u

Total volume of April and May is combined repeated identity. Make the total volume of April and May the same. LCM of 2 and 3 is 6.

Volume of less detergent syrup in the bottle used in May than March
= 15 u - 4 u
= 11 u

11 u = 0.99 

1 u = 0.99 ÷ 11 = 0.09

Amount of detergent in the bottle at first
= 21 u
= 21 x 0.09
= 1.89 ℓ

1 ℓ = 1000 mℓ

Amount of detergent in the bottle at first
= 1.89 x 1000
= 1890 mℓ

Answer(s): 1890 mℓ