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 30ft, 25ft, 40ft.

Use Heron’s formula to find the triangle’s area. The semiperimeter is (30 + 25 + 40) ÷ 2 = 47.5 ft, so the area is √[47.5 × 17.5 × 22.5 × 7.5] ≈ 375 square feet. At 1 cow per 50 square feet, 375 ÷ 50 = 7.5, so the pen fits 7 whole cows. The correct choice is 7 cows.

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