PSLE
Lynn had a bottle of soy milk. She drank 180 mℓ of soy milk in the afternoon and ²₇ of remaining soy milk at night. After that, there was ¹₂ 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 - ²₇
= ⁵₇

The remaining soy milk left in the end is equal to ¹₂ of the bottle of soy milk.
Make numerators the same.
LCM of 5 and 1 is 5.
 
⁵₇ of the remaining soy milk = ¹₂ of the total soy milk
⁵₇ of the remaining soy milk = ⁵₁₀ of the total soy milk

Volume of soy milk that she drank in the afternoon
= 10 u - 7 u
= 3 u

3 u = 180

1 u = 180 ÷ 3 = 60

Volume of soy milk that she drank at night
= 2 u
= 2 x 60
= 120 mℓ

Answer(s): 120 mℓ