Below is an instruction that describes a task. Write a response that appropriately completes the request in English. Please answer in English.

### Instruction:
Jacob's water tank can hold up to 50 liters of water. Jacob collects water from the river and rain to fill his water tank. He can collect 800 milliliters of water from the rain and 1700 milliliters of water from the river every day. How many days does Jacob need to fill up his water tank?

### Response:
Since 1 liter is equal to 1000 milliliters, then 50 liters is equal to 50 x 1000 = <<50*1000=50000>>50,000 milliliters of water.
Jacob collects 800+1700= <<800+1700=2500>>2500 milliliters of water from the river and rain every day.
Therefore Jacob needs 50,000/2500=<<50000/2500=20>>20 days to fill his water tank.
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