Question

Bob is trying to decide between two cell phone plans. Plan A has no flat fee, but the user must pay $10 cents per minute on the phone. Plan B requires a one-time fee of $20 but only requires a payment of $5 cents per minute on the phone. What is the minimum whole number of minutes Bob has to use the phone for to make Plan B the cheaper plan?

PLZ HELP ASAP
Thanks

Answer 1

$ per min is a rate. you multiple by minutes to get dollars.

A = 10x
B = 5x + 20

set them equal to find minutes, x.

10x = 5x + 20
10x - 5x = 20
5x = 20

x = 4

Answer 2

Let x be the number of minutes that Bob anticipates using. Plan A costs 10x cents, while Plan B costs 2000 + 5x cents. We therefore have the inequality

2000+5x < 10x

2000 < 5x

400 < x.

The smallest integer x such that 400 < x is 401. Therefore, Bob must use at least 401 minutes to make Plan B cheaper.