Dunno if this is correct:
We know the perimeter of a circle (or circumference) is \(2\pi R\). So that means if we want to find the area of a semi-circle, we have to divide the perimeter by 2:
Radius (R) = 5.
So it's 2 * 3.142 * 5 = 31.42.
We have to divide this by 2 so we can get our final answer:
31.42 / 2 = 15.71.
Ahh I noticed why mine was incorrect, I only did the curvy side and forgot about the bottom:
15.71 + 10 = 25.71
Well, if we know the the total trip is 2880 km, and they drive 240km per day, 2880/240 = 12. So that means (i think) they drove 12 days in total. And they stayed in Montreal for 6 days. 12 + 6 = 18 days. So 18 days in total? That doesn't seem right. I'm assuming that the driving distance from Halifax to Montreal was 1440 km, and from Montreal and back to Halifax was also 1440km.
So we know that 8 girls brought lunchboxes. And 4 didn't. And we also know that 2 boys brought a lunchbox, but 6 didn't.
This means that there are 10 kids in total who brought a lunchbox. 10/20 = 1/2. So if you choose a random child from the class, you have a 1/2 chance of getting a kid that has a lunchbox.
Please reply if I'm wrong.