Diana purchased a bottle of grapefruit syrup to make drinks. She used ²₅ of the syrup in February. She then used the remaining syrup in March and April in the ratio 1 : 3. Given that the amount of the grapefruit syrup used in February was 0.15 ℓ more than that in March, how many millilitres of grapefruit syrup did the bottle contain at first?

February	March	April	Total
2x4	3x4		5x4
	1x3	3x3
8 u	3 u	9 u	20 u

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

Volume of more grapefruit syrup in the bottle used in February than March
= 8 u - 3 u
= 5 u

5 u = 0.15 

1 u = 0.15 ÷ 5 = 0.03

Amount of grapefruit syrup in the bottle at first
= 20 u
= 20 x 0.03
= 0.6 ℓ

1 ℓ = 1000 mℓ

Amount of grapefruit syrup in the bottle at first
= 0.6 x 1000
= 600 mℓ

Answer(s): 600 mℓ