Suppose you make a 4-minute local call using a calling card and are charged 7.6 cents. The cost of a local call varies directly with the length of the call. How much more will it cost to make a 30-minute local call?
-Which quantity is the dependent quantity?
-How does the word "more" affect the method needed to solve the problem?

Question

Suppose you make a 4-minute local call using a calling card and are charged 7.6 cents. The cost of a local call varies directly with the length of the call. How much more will it cost to make a 30-minute local call?
-Which quantity is the dependent quantity?
-How does the word "more" affect the method needed to solve the problem?

anonymous · Answer

It would cost 49.4 more cents to make a 30-minute phone call. The dependent quantity is the cost, it depends on how long the call is. The word "more" in the problem shows that it doesn't want to know the cost of a 30 minute phone call, but rather how much more it would be compared to the 4-minute phone call. It means that after you have found how much it costs to make the 30-minute phone call, you have to subtract the 7.6 cents from it to find out how much more it costs.