Question

Three-quarters of the boats in the marina are white, 4/7 of the remaining boats are blue, and the rest are red. If there are 9 red boats, how many boats are in the marina?

Answer 1

84 because if 1/4 of the boats are divided into sevenths, that makes the whole marina a 28 part item. 3/28 are red so 84 is the total number of boats.

Answer 2

Answer: There are 84 boats.

Explanation:

Let be "x" the number of boats in the marina.

According to the exercise,
`(3)/(4)` of the boats are white. This is:

`(3)/(4)x`

You know that
`(4)/(7)` of the remaining boats are blue. This is:

`(1-(3)/(4))((4)/(7))x=(1)/(7)x`

And the rest of the boats are red and there are 9 of them.

Knowing this, you can write the following expression:

`x-(3)/(4)x-(1)/(7)x=9`

Finally, you must solve for "x":

`(3)/(28)x=9\\\\x=(9)((28)/(3))\\\\x=84`