if sound can travel through solid , liquid , and gas then  how can planting trees in residential areas  , reduce noise pollution as the sound can travel through the tree which is solid 

Dear student,
Please find below the answer:

Trees block or cause hindrance in the propagation of the sound waves. They absorb the noise by a considerable amount. Thus planting trees help us to reduce noise pollution.
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Hope this clears your doubt.
Regards.