Problema Solution
A long distance phone call costs $10.00 for the first ten minutes and $0.75 for each additional 30 seconds. If Andre has $16.65, how long can he talk for?
Answer provided by our tutors
let x = the total minutes that Andre talked then
the cost for the first 10 minutes + the cost of the rest of the time = the total of money that Andre has
10 + ((x - 10)*2)*0.75 = 16.65
by solving this equations we find
x = 433/30 = 14 13/30 min = 14 min 26 seconds
since after the first 10 minutes every 30 seconds are charged - he can talk 14 min
indeed
10 + 4*2*0.75 = 16
for 14 min he will spend $16 and will be left with $0.65 and 0.65 < 0.75 so he can not talk another 30 seconds.
Andre can talk 14 minutes.