For her phone, Halima pays a monthly fee of 18 AED and she pays an additional 5 fils per minute of use. The least she has been charged in a month is 71.90 AED. What is the minimum number of minutes she has used on her phone in a month?

1078 minutes

Step-by-step explanation:

18 + 0.05x = 71.90

0.05x = 71.90 - 18

0.05x = 53.9

x = 53.9/0.05

x = 1078 minutes

1078

Step-by-step explanation:

(b) 240

step-by-step explanation:

first, we use the pythagorean formula using the given side lengths to find x. then we use x to find the side lengths. then we add the side lengths to find the perimeter.

pythagorean theorem formula:

a^2 + b^2 = c^2

(x - 20)^2 + (x - 40)^2 = x^2

x^2 - 40x + 400 + x^2 - 80x + 1600 = x^2

x^2 -120x + 2000 = 0

(x - 100)(x - 20) = 0

x - 100 = 0 or x - 20 = 0

x = 100 or x = 20

we see that the solution x = 20 must be discarded because it will give a negative side length and a side length of 0. the only valid solution is x = 100.

perimeter = sum of the lengths of the sides

perimeter = x + x - 20 + x - 40

perimeter = 3x - 60

replace x with 100.

perimeter = 3(100) - 60

perimeter = 300 - 60

perimeter = 240