PSLE
Mrs Toh had a bottle of wine. She used an equal amount of wine each day. At the end of the fifth day, she had 2430 mℓ of wine left. At the end of the eighth day, she had three-quarters of the bottle of wine left. How many litres of wine were there in the bottle at first?
Fraction of wine used after three-quarters of the bottle was left
= 1 - ³₄
= ¹₄

¹₄ of the bottle → 8 days
1 bottle → 8 ÷ ¹₄ = 8 x ⁴₁ =  32 days

It takes 32 days to finish the whole bottle.

Number of days to use 2430 mℓ of wine
= 32 - 5
= 27

27 days → 2430 mℓ

1 day → 2430 ÷ 27 = 90 mℓ

32 days → 32 x 90 = 2880 mℓ

1000 mℓ = 1 ℓ

2880 mℓ = 2880 ÷ 1000 = 2.88 ℓ

Volume of wine in the bottle at first = 2.88 ℓ

Answer(s): 2.88 ℓ