PSLE
Mrs Seow 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 1600 mℓ of maple syrup left. At the end of the eighth day, she had two-thirds 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 two-thirds of the bottle was left
= 1 - ²₃
= ¹₃

¹₃ of the bottle → 8 days
1 bottle → 8 ÷ ¹₃ = 8 x ³₁ =  24 days

It takes 24 days to finish the whole bottle.

Number of days to use 1600 mℓ of maple syrup
= 24 - 4
= 20

20 days → 1600 mℓ

1 day → 1600 ÷ 20 = 80 mℓ

24 days → 24 x 80 = 1920 mℓ

1000 mℓ = 1 ℓ

1920 mℓ = 1920 ÷ 1000 = 1.92 ℓ

Volume of maple syrup in the bottle at first = 1.92 ℓ

Answer(s): 1.92 ℓ