PSLE
Mrs Hun had a bottle of wine. She used an equal amount of wine each day. At the end of the fifth day, she had 1710 mℓ of wine left. At the end of the eighth day, she had two-thirds of the bottle of wine left. How many litres of wine were there in the bottle at first?
Fraction of wine used after two-thirds of the bottle was left
= 1 - ²₃
= ¹₃

¹₃ of the bottle → 8 days
1 bottle → 8 ÷ ¹₃ = 8 x ³₁ =  24 days

It takes 24 days to finish the whole bottle.

Number of days to use 1710 mℓ of wine
= 24 - 5
= 19

19 days → 1710 mℓ

1 day → 1710 ÷ 19 = 90 mℓ

24 days → 24 x 90 = 2160 mℓ

1000 mℓ = 1 ℓ

2160 mℓ = 2160 ÷ 1000 = 2.16 ℓ

Volume of wine in the bottle at first = 2.16 ℓ

Answer(s): 2.16 ℓ