Answer:
$21.2
Step-by-step explanation:
From the problem given, we express them as algebra so that we can easily solve;
the total charge on a call greater than 120min is given as;
120x + y(n - 120) = total cost of call
where n is the number of minutes which is greater than 120;
- Ethan paid $26.80 for 175 mins
n = 175min here;
120x + y(175 - 120) = 26.80
120x + 55y = 26.80 ----- (I)
- $32.40 for 210 minutes
n = 210min
120x + y(210 - 120) = 32.4
120x + 90y = 32.4 ----- (II)
Now let us solve both equations for y and x;
120x + 55y = 26.80 ----- (I)
120x + 90y = 32.4 ----- (II)
subtract the two equations;
90y - 55y = 32.4 - 26.8
35y = 5.6
y = = 0.16cents
then x;
120x = 26.8 - 55y from equation I
120x = 26.8 - 55(0.16)
120x = 18
x = = 0.15cents
Find the cost of 140min of talk time;
n =140min;
= 120(0.15) + 0.16(140 - 120)
= 18 + 0.16(20)
= 18 + 3.2
= $21.2