Question

A phone company ofders two monthly plans. Plan A cost $18 plus an additional $0.18 for each minute calls. Plan B costs $22 plus an additional $0.13 for each minute of callsFor what amount of calling do the two plans cost the same?minuteswhat is the cost when the two plans cost the same?$

Answer 1

80 minutes. $32.4

1) Let's write those plans, as functions:

Plan A

P(m)= 18 + 0.18m

Plan B

C(m) = 22 + 0.13m

2) To find out what amount of calling costs the same, we need to find a common value for m, (minutes). Then we can equate those

18 + 0.18m = 22 +0.13m Subtract 18 and 0.13m from both sides

0.18m -0.13m = 22 -18

0.05m = 4 Divide both sides by 0.05

0.05/0.05 m = 4/0.05

3) The cost, when two plans c

m =80

3) Hence, calling 80 minutes per month is the same cost for both plans, we just need to plug into that m=80

Since Plan A for 80 minutes is the same as Plan B

Plan A:

P(m)= 18 + 0.18m

P(80) = 18 +0.18(80)

P(80) = 18 +14.4

P(80) =32.4

Just to check:

Plan B

C(m) =22 +0.13m

C(80) =22 +0.13(80)

C(80) =22+10.4

C(80) = 32.4

Both plans will charge $32.40