SOLUTION: I really cannot figure this out! Please help!!! A disk jockey must play 12 commercial spots during one hour of a radio show. Each comercial is either 30 seconds or 60 seconds lo

Algebra ->  Equations -> SOLUTION: I really cannot figure this out! Please help!!! A disk jockey must play 12 commercial spots during one hour of a radio show. Each comercial is either 30 seconds or 60 seconds lo      Log On


   

Question 221017: I really cannot figure this out! Please help!!!
A disk jockey must play 12 commercial spots during one hour of a radio show. Each comercial is either 30 seconds or 60 seconds long. If the total commercial time during one hour is 8 minutes, how many 30-sec commercials were played that hour? How many 60-sec commercials?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
A disk jockey must play 12 commercial spots during one hour of a radio show.
Each comercial is either 30 seconds or 60 seconds long.
If the total commercial time during one hour is 8 minutes, how many 30-sec commercials were played that hour?
How many 60-sec commercials?
:
Let x = no. of 30 sec
let y = no. of 60 sec
:
Convert 8 min to 480 second
:
Two equations:
x + y = 12
arrange for substitution
x = 12-y
:
30x + 60y = 480
simplify, divide by 30
x + 2y = 16
;
Replace x with (12 - y)
12 - y + 2y = 16
-y + 2y = 16 - 12
y = 4 ea 60 sec commercials
and
x = 12 - 4
x = 8 ea 30 sec commercials
;
Check solution in 2nd original equation
30(8) + 60(4) =
240 + 240 = 480 sec = 8 min