PSLE
Mrs Zhang had a bottle of maple syrup. She used an equal amount of maple syrup each day. At the end of the eighth day, she had 1000 mℓ of maple syrup left. At the end of the twelfth day, she had one-third of the bottle of maple syrup left. How many litres of maple syrup were there in the bottle at first?
Fraction of maple syrup used after one-third of the bottle was left
= 1 - ¹₃
= ²₃

²₃ of the bottle → 12 days
1 bottle → 12 ÷ ²₃ = 12 x ³₂ =  18 days

It takes 18 days to finish the whole bottle.

Number of days to use 1000 mℓ of maple syrup
= 18 - 8
= 10

10 days → 1000 mℓ

1 day → 1000 ÷ 10 = 100 mℓ

18 days → 18 x 100 = 1800 mℓ

1000 mℓ = 1 ℓ

1800 mℓ = 1800 ÷ 1000 = 1.8 ℓ

Volume of maple syrup in the bottle at first = 1.8 ℓ

Answer(s): 1.8 ℓ