Alyssa used half of the candles, which is 1/2*40 = <<1/2*40=20>>20 candles

The number of candles that remained is 40-20 = <<40-20=20>>20

Chelsea used 70% of the remaining candles, a total of 70/100*20 = <<70/100*20=14>>14 candles.

The total number of candles in the room now is 40 - 20-14 = <<40-20-14=6>>6

# Answer

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<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Alyssa and Chelsea jointly bought 40 candles to decorate their room. Alyssa used half of them, and Chelsea used 70% of the remaining candles. How many candles are there in the room now?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
6
Alyssa and Chelsea jointly bought 40 candles to decorate their room. Alyssa used half of them, and Chelsea used 70% of the remaining candles. How many candles are there in the room now?
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