Question

The area of a rectangle is 70 m², and the length of the rectangle is 11 m less than three times the width. Find the dimensions of the rectangle
Length: m
Width: m

Answer 1

Step-by-step explanation:

the area of a rectangle is

length × width

in our case

length × width = 70 m²

length = 3×width - 11

we can use this second equation in the first and get

(3×width - 11) × width = 70

3×width² - 11×width - 70 = 0

the general solution to a quadratic equation is

x = (-b ± sqrt(b² - 4ac))/(2a)

in our case

a = 3

b = -11

c = -70

x = (11 ± sqrt((-11)² - 4×3×-70))/(2×3) =

= (11 ± sqrt(121 + 840))/6 =

= (11 ± sqrt(961))/6

x1 = (11 + 31)/6 = 42/6 = 7

x2 = (11 - 31)/6 = -20/6 = -10/3

the negative solution is not applicable for a length in an object.

so, only x1 = 7 m is our solution.

the width of the rectangle is 7 m.

the length = 3×width - 11 = 3×7 - 11 = 21-11 = 10 m