Q. The length of an 8000 square foot rectangular gymnasium is 20 feet greater than its width. What is its width, in feet?
Define Variables: Let's denote the width of the gymnasium as w (in feet). According to the problem, the length is 20 feet greater than the width, so we can denote the length as w+20 (in feet). The area of a rectangle is given by the formula length × width. We are given that the area of the gymnasium is 8000 square feet. So, we can set up the equation:Area = width × length8000=w×(w+20)
Expand Equation: Now we need to solve the quadratic equation for w. First, we expand the right side of the equation:8000=w2+20w
Set to Zero: To solve the quadratic equation, we need to set it to zero by moving all terms to one side:w2+20w−8000=0
Apply Quadratic Formula: We can attempt to factor the quadratic equation, but it does not factor nicely. Therefore, we will use the quadratic formula to solve for w. The quadratic formula is given by:w=2a−b±b2−4acIn our equation, a=1, b=20, and c=−8000.
Substitute Values: We substitute the values of a, b, and c into the quadratic formula:w=2(1)−20±202−4(1)(−8000)w=2−20±400+32000w=2−20±32400
Calculate Discriminant: We calculate the discriminant (32400) and simplify the expression:w=2−20±180
Find Positive Solution: Since we are looking for a positive width, we take the positive solution of the quadratic formula:w=(−20+180)/2w=160/2w=80
Check Solution: We have found the width of the gymnasium to be 80 feet. We should check that this width gives us the correct area when multiplied by the length (which is 20 feet greater than the width).Length = w+20=80+20=100 feetArea = width × length = 80 feet ×100 feet = 8000 square feetThis matches the given area, so our solution is correct.
More problems from Pythagorean Theorem and its converse