PSLE
Gem had a bottle of coffee. She drank 450 mℓ of coffee in the morning and ³₇ of remaining coffee in the evening. After that, there was ¹₃ a bottle of coffee left. How much of the coffee did she drink in the evening?
Fraction of the remaining coffee left in the end
= 1 - ³₇
= ⁴₇

The remaining coffee left in the end is equal to ¹₃ of the bottle of coffee.
Make numerators the same.
LCM of 4 and 1 is 4.
 
⁴₇ of the remaining coffee = ¹₃ of the total coffee
⁴₇ of the remaining coffee = ⁴₁₂ of the total coffee

Volume of coffee that she drank in the morning
= 12 u - 7 u
= 5 u

5 u = 450

1 u = 450 ÷ 5 = 90

Volume of coffee that she drank in the evening
= 3 u
= 3 x 90
= 270 mℓ

Answer(s): 270 mℓ