Question

Marcia can make 5 candles in an hour. Kevin can make only 4 candles in an hour, but he already has 7 completed candles. how can Marcia use a system of equations to determine when she will have the same number of candles as Kevin?

Answer 1

After 7 hours.

Explanation:

Let Marcia and Kevin can make candles in h hours.

Now Marcia can make 5 candles per hour

so total number of candles made = 5h

similarly Kevin can make only 4 candles in one hour.

So total candles made in h hours = 4h

But Kevin has already completed 7 candles so total candles made by Kevin = (4h + 7)

Now it is given that both Marcia and Kevin made same number of candles in h hours.

so 5h = (4h + 7)

5h - 4h = 7

h = 7

After 7 hours candles made by both Marcia and Kevin will be same.

Answer 2

Marcia can write an expression for the number of candles she will have at the end of "h" hours. She can also write an expression for the number of candles Kevin will have at the end of "h" hours. She can set the two expressions equal to each other and solve for "h", the number of hours until each has the same number of candles.


5h = 4h+7
h = 7 … subtract 4h from each side
In 7 hours, each will have the same number of candles.