A farmer divides his herd of $mathrm{n}$ cows among his four sons, so that the first son gets one-half the herd, the second one-fourth, the third son $frac{1}{5}$ and the fourth son 7 cows. Then the value of $n$ is

According to the question, $frac{n}{2}+frac{n}{4}+frac{n}{5}+7=n$

$Rightarrow frac{10 n+5 n+4 n}{20}+7=n$

$Rightarrow frac{19 n}{20}+7=n$

$Rightarrow n-frac{19 n}{20}=7$

$Rightarrow frac{n}{20}=7$

$Rightarrow n=20 imes 7=140$