Question

Sean drank 3/5 of the water in his water bottle. He accidentally spilled 1/4 of the remaining water. As a result, he had 90 millilitres of water left in his water bottle. How much water did Sean have at first? Give your answer in millilitres

Answer 1

Let the total amount of water in bottle be x.
=> x - 3/5x - 1/4 (x - 3/5x) = 90 ml
=> ((5x - 3x)/5) - 1/4 ((5x - 3x)/5) = 90 ml
=> (2x/5) - 1/4 * (2x/5) = 90 ml
=> ((4 - 1) 2x)/(4 * 5) = 90 ml
=> (3 * 2x)/20 = 90 ml
=> 6x = 90 * 20 = 1800 ml
x = 1800/6 = 300 ml