Question

Your cell phone company offer two text-messaging plans. On plan costs $.25 per text message, plus a monthly fee of $9. The other plan costs $.40 per text message with no monthly fee. For how many text messages will the cost be the same amount? What is that cost?

Answer 1

Explanation:

m = number of messages

cost_plan1(m) = 9 + 0.25×m

cost_plan2(m) = 0 + 0.40×m = 0.4×m

to find the number of messages for which both costs are the same, we only need to set both functions to have the equal result and solve for m :

9 + 0.25×m = 0.4×m

9 = 0.15×m

m = 9/0.15 = 60

60 × 0.4 = $24

for 60 messages both plans will cost the same : $24