PSLE
Mrs Yee 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 400 mℓ of maple syrup left. At the end of the sixth day, she had one-quarter 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-quarter of the bottle was left
= 1 - ¹₄
= ³₄

³₄ of the bottle → 6 days
1 bottle → 6 ÷ ³₄ = 6 x ⁴₃ =  8 days

It takes 8 days to finish the whole bottle.

Number of days to use 400 mℓ of maple syrup
= 8 - 4
= 4

4 days → 400 mℓ

1 day → 400 ÷ 4 = 100 mℓ

8 days → 8 x 100 = 800 mℓ

1000 mℓ = 1 ℓ

800 mℓ = 800 ÷ 1000 = 0.8 ℓ

Volume of maple syrup in the bottle at first = 0.8 ℓ

Answer(s): 0.8 ℓ