Emma purchased a bottle of grapefruit syrup to make drinks. She used ³₇ of the syrup in April. She then used the remaining syrup in May and June in the ratio 1 : 2. Given that the amount of the grapefruit syrup used in April was 0.4 ℓ more than that in May, how many millilitres of grapefruit syrup did the bottle contain at first?

April	May	June	Total
3x3	4x3		7x3
	1x4	2x4
9 u	4 u	8 u	21 u

Total volume of May and June is combined repeated identity.  Make the total volume of May and June the same.  LCM of 4 and 3 is 12.

Volume of more grapefruit syrup in the bottle used in April than May
= 9 u - 4 u
= 5 u

5 u = 0.4 

1 u = 0.4 ÷ 5 = 0.08

Amount of grapefruit syrup in the bottle at first
= 21 u
= 21 x 0.08
= 1.68 ℓ

1 ℓ = 1000 mℓ

Amount of grapefruit syrup in the bottle at first
= 1.68 x 1000
= 1680 mℓ

Answer(s): 1680 mℓ