Human: John buys 1000 balloons. Each balloon holds 10 liters of air. If he buys 500-liter tanks of gas, how many tanks does he need to buy to fill all the balloons? Assistant: 
How many liters of gas does John need? ** He needs 1000*10=<<1000*10=10000>>10000 liters of gas
How many tanks does John need? ** So he needs 10000/500=<<10000/500=20>>20 tanks
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