Question
At first, Tank Y and Tank Z contained 0.5 ℓ and 2.1 ℓ of water respectively. Some water from Tank Z was poured into Tank Y with no water spilling over. In the end, there was as much water in Tank Y as in Tank Z. How much water was poured from Tank Z to Tank Y?
3 m

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At first, Tank Y and Tank Z contained 0.5 ℓ and 2.1 ℓ of water respectively. Some water from Tank Z was poured into Tank Y with no water spilling over. In the end, there was as much water in Tank Y as in Tank Z. How much water was poured from Tank Z to Tank Y?