PSLE
Hazel had a bottle of coffee. She drank 550 mℓ of coffee in the afternoon and ³₅ of remaining coffee at night. After that, there was ¹₈ a bottle of coffee left. How much of the coffee did she drink at night?
Fraction of the remaining coffee left in the end
= 1 - ³₅
= ²₅

The remaining coffee left in the end is equal to ¹₈ of the bottle of coffee.
Make numerators the same.
LCM of 2 and 1 is 2.
 
²₅ of the remaining coffee = ¹₈ of the total coffee
²₅ of the remaining coffee = ²₁₆ of the total coffee

Volume of coffee that she drank in the afternoon
= 16 u - 5 u
= 11 u

11 u = 550

1 u = 550 ÷ 11 = 50

Volume of coffee that she drank at night
= 3 u
= 3 x 50
= 150 mℓ

Answer(s): 150 mℓ