PSLE
Mrs Lim had a bottle of wine. She used an equal amount of wine each day. At the end of the fifth day, she had 1840 mℓ of wine left. At the end of the seventh 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 → 7 days
1 bottle → 7 ÷ ¹₄ = 7 x ⁴₁ =  28 days

It takes 28 days to finish the whole bottle.

Number of days to use 1840 mℓ of wine
= 28 - 5
= 23

23 days → 1840 mℓ

1 day → 1840 ÷ 23 = 80 mℓ

28 days → 28 x 80 = 2240 mℓ

1000 mℓ = 1 ℓ

2240 mℓ = 2240 ÷ 1000 = 2.24 ℓ

Volume of wine in the bottle at first = 2.24 ℓ

Answer(s): 2.24 ℓ