PSLE
Mrs Fong had a bottle of maple syrup. She used an equal amount of maple syrup each day. At the end of the fourth day, she had 720 mℓ of maple syrup left. At the end of the sixth day, she had half 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 half of the bottle was left
= 1 - ¹₂
= ¹₂

¹₂ of the bottle → 6 days
1 bottle → 6 ÷ ¹₂ = 6 x ²₁ =  12 days

It takes 12 days to finish the whole bottle.

Number of days to use 720 mℓ of maple syrup
= 12 - 4
= 8

8 days → 720 mℓ

1 day → 720 ÷ 8 = 90 mℓ

12 days → 12 x 90 = 1080 mℓ

1000 mℓ = 1 ℓ

1080 mℓ = 1080 ÷ 1000 = 1.08 ℓ

Volume of maple syrup in the bottle at first = 1.08 ℓ

Answer(s): 1.08 ℓ