Zoe purchased a bottle of mango syrup to make drinks. She used ⁵₇ of the syrup in March. She then used the remaining syrup in April and May in the ratio 1 : 4. Given that the amount of the mango syrup used in March was 1.38 ℓ more than that in April, how many millilitres of mango syrup did the bottle contain at first?

March	April	May	Total
5x5	2x5		7x5
	1x2	4x2
25 u	2 u	8 u	35 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 5 is 10.

Volume of more mango syrup in the bottle used in March than April
= 25 u - 2 u
= 23 u

23 u = 1.38 

1 u = 1.38 ÷ 23 = 0.06

Amount of mango syrup in the bottle at first
= 35 u
= 35 x 0.06
= 2.1 ℓ

1 ℓ = 1000 mℓ

Amount of mango syrup in the bottle at first
= 2.1 x 1000
= 2100 mℓ

Answer(s): 2100 mℓ