12. kWh: 52,344 – 50,361 = 1,983
Cost: 1,983 × $0.095 = $188.39
Delivery: 30 days @ $0.18 = $5.40
14. Let x represent the amount still owed at the end
of the year. Multiply the monthly amount paid by
12 and add the amount still owed.
x + 12($223) = x + $2,676
15. Since they used less than they were billed for,
16. Substitute 500 for w, 25 for m, and $0.125 for c.
25
500 60 ($0.125)
⎛⎞
⎜⎟
4,200(3)
$0.11 1,000
⎛
⎜
⎝⎠
⎞
⎟
= $1.386
Round to the nearest ten cents, $1.40.
17b. $1.40 × 365 = $511
understanding from Example 5, substitute
$1,100 for c, 36 for p, and $510 for r.
36 ($510)
100
⎡⎤
⎢⎥
⎢⎥
⎣⎦
18. $4.173 $1.192
$1.192
19a. 1 kilowatt-hour is the same as 1,000 watt-hours,
so if 3.413 BTU’s are equivalent to 1 watt-hour,
3.413 × 1,000 = 3,413 BTU’s are equivalent to
Lesson 10-2 Electronic Utilities
Check Your Understanding (Example 1)
The first 3 minutes are $0.35. Subtract to find the
The call went 1
94 minutes over the initial
Check Your Understanding (Example 2)
The first line of the piecewise function represents
the cost of a call that is 5 minutes or less, which is
65 cents. In the second line of the function, use
shown below.
0 65 when 3
0 65 0 22 3 when 3 and is an integer
m
cm m m m
≤
⎧
⎪
=+ − >
⎨
$.
( ) $. $. ( )