PSLE
Mrs Tan had a bottle of cooking wine. She used an equal amount of cooking wine each day. At the end of the sixth day, she had 1700 mℓ of cooking wine left. At the end of the tenth day, she had three-quarters of the bottle of cooking wine left. How many litres of cooking wine were there in the bottle at first?
Fraction of cooking wine used after three-quarters of the bottle was left
= 1 - ³₄
= ¹₄

¹₄ of the bottle → 10 days
1 bottle → 10 ÷ ¹₄ = 10 x ⁴₁ =  40 days

It takes 40 days to finish the whole bottle.

Number of days to use 1700 mℓ of cooking wine
= 40 - 6
= 34

34 days → 1700 mℓ

1 day → 1700 ÷ 34 = 50 mℓ

40 days → 40 x 50 = 2000 mℓ

1000 mℓ = 1 ℓ

2000 mℓ = 2000 ÷ 1000 = 2 ℓ

Volume of cooking wine in the bottle at first = 2 ℓ

Answer(s): 2 ℓ