Erika purchased a bottle of pear syrup to make drinks. She used ⁵₈ of the syrup in April. She then used the remaining syrup in May and June in the ratio 1 : 3. Given that the amount of the pear syrup used in April was 1.02 ℓ more than that in May, how many millilitres of pear syrup did the bottle contain at first?

April	May	June	Total
5x4	3x4		8x4
	1x3	3x3
20 u	3 u	9 u	32 u

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

Volume of more pear syrup in the bottle used in April than May
= 20 u - 3 u
= 17 u

17 u = 1.02 

1 u = 1.02 ÷ 17 = 0.06

Amount of pear syrup in the bottle at first
= 32 u
= 32 x 0.06
= 1.92 ℓ

1 ℓ = 1000 mℓ

Amount of pear syrup in the bottle at first
= 1.92 x 1000
= 1920 mℓ

Answer(s): 1920 mℓ