True.
At night, the amount of CO2 in atmosphere increases the density of atmosphere. Since, Speed of sound is inversely proportional to the square root of density.
Hence, speed of sound is greater during...
Correct option is (D) \(7\,\frac{1}{2}\) hrs
\(\because\) Time taken to fill a \(50\,l\) of tank = 5 hours
\(\therefore\) Time taken to fill a \(75\,l\) of tank \(=\frac5{50}\times75\;hours\)
\(=\frac{75}{10}\;hours\) = 7.5 hours
= 7 hours + \(\frac12\) hours
= \(7\frac12\) hours