Question

an eco is heard on a day when temperature is about 22 degree Celsius will the Eco be heard sooner or later in the temperature falls to 4 degree celcius

Answer 1

the echo will be heard later
reason
when the temperature decreases the air pressure increases therefore the doubt will take more time to travell

Answer 2

the echo will be heard later as sound is directly proportional to temperature and as temperature increases the sound will be faster. so as 4degrees is less than 22 degrees it will be heard later.

hope it helps.....