Answer:
Center: (-5,10)
Radius: 2
Step-by-step explanation:
The equation of the circle in center-radius form is:
Where the point (h,k) is the center of the circle and "r" is the radius.
Subtract 121 from both sides of the equation:
Add 10x to both sides:
Make two groups for variable "x" and variable "y":
Complete the square:
Add 
inside the parentheses of "x".
Add 
inside the parentheses of "y".
Add 
and 
to the right side of the equation.
Then:
Rewriting, you get that the equation of the circle in center-radius form is:
You can observe that the radius of the circle is:
And the center is:
Answer: 13
Althoug each round trip takes 9 minutes and can carry 5 people on the boat, you can not just divide the 20 minutes time by 9 and multiply by 5 to find the number of people that are saved without getting wet.
First trip:
5 people take the boat to the island but only 4 can stay, because one has to return with the boat to the ship to rescue other 4 people.
So, when 9 minutes have passed, 4 people are safe on the island and the boat is again by the ship.
Second trip:
In the second trip, other 4 people are rescued,along with "sailor" who returned in the boat to rescue them.
When it has passed 18 minutes, the boat is next to the ship agin to carry other 4 people before the boat sinks.
This is the last trip before the boat sinks. So, the total number of passengers rescued is 4 + 4 + 5 = 13
3:20 then 3:40 then 4:00 for both
