A farmer can fit 1 cow per 50 square feet of area inside of a pen. Determine how many cows he can fit inside the area of triangle shaped pen with sides of length 30 ft, 25 ft, 40 ft.

First, determine the area of the triangle. When all sides of the triangle are given, you can determine its area through the semi-perimeter. This is the half of a perimeter.

s = (30 + 25 + 40) / 2

s = 47.5

Then, we apply the Heron's formula:

A = square root [s (s-a) (s-b) (s-c) ], where a, b and c are side lengths of the triangle

A = square root [47.5 (47.5-30) (47.5-25) (47.5-40) ]

A = 374.53 sq feet

To find the number of cows, divide the area by 50:

Number of cows = 373.53 ft2 / 50 ft2 per cow

Number of cows = 7.4906

The estimated number of cow is 7.