Question 75285

THE EQUALITY SIGN MUST BE A <= SIGN BECAUSE WE ARE TOLD THAT THE COST CAN'T EXCEED $3.00.  AT LEAST YOU GAVE IT A SHOT BUT I'M NOT SURE THAT I CAN FOLLOW WHAT YOU DID.  SEE WHAT YOU THINK ABOUT MY APPROACH:

FIRST, I'M ASSUMING YOU MEANT $0.36 AND NOT $0.036

Anyway, let's deal in pennies to make life more simple

Let x=number of minutes a person can talk without exceeding 300 (pennies)
First minute cost=36 cents
additional minutes cost 21 cents per minute

So our equation is:

36+21(x-1)<= 300 ----------------this is what I get (Note that I subtracted out the first minute)
36+21x-21 <=300
21x+15 <=300 subtract 15 from both sides
21x+15-15 <=300-15 collect like terms

21x <=285  divide both sides by 21

x<=13.5714 or 13 minutes (We can't round up because x is LESS THAN OR EQUAL TO 13.5714).  Also, if you try 14, you will find that it breaks the bank. 

ck
36 +12*21<=300
36+252<=300
288 <= 300  another minute would cost 21 cents--no can do!


Hope this helps----ptaylor