PSLE
Xylia had a bottle of soy milk. She drank 520 mℓ of soy milk in the afternoon and ³₅ of remaining soy milk at night. After that, there was ¹₉ a bottle of soy milk left. How much of the soy milk did she drink at night?
Fraction of the remaining soy milk left in the end
= 1 - ³₅
= ²₅

The remaining soy milk left in the end is equal to ¹₉ of the bottle of soy milk.
Make numerators the same.
LCM of 2 and 1 is 2.
 
²₅ of the remaining soy milk = ¹₉ of the total soy milk
²₅ of the remaining soy milk = ²₁₈ of the total soy milk

Volume of soy milk that she drank in the afternoon
= 18 u - 5 u
= 13 u

13 u = 520

1 u = 520 ÷ 13 = 40

Volume of soy milk that she drank at night
= 3 u
= 3 x 40
= 120 mℓ

Answer(s): 120 mℓ