De un depósito se gasta primero la mitad del agua, y luego la cuarta parte de lo que quedaba. Al final, quedan 12 litros. Hallar la capacidad del depósito.

5/8 fraction of the deposit has been spent, which is 20 liters

Let "a" be the initial amount of water, then first half the water is used: then a / 2 of water is used and the other half is left at / 2 * (1/4), then the fourth part is used: then 1/8 * a is used, so now it remains: a / 2 - a / 8 = 3/8 * a, so 5/8 * a has been used, then what remains are 12 liters:

3/8 * a = 12 L

a = 12 L * 8/3 = 32 L

Wasted: 32 L - 12 L = 20 L

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one that is bigger than 3 1/2