Not so sure about the second one, but the first one is pretty simple:
The area of a circle = pi x radius^2
Since you need to find the area of the entire dvd, I'm assuming they mean if the hole in the center wasn't there, so add that to the diameter.
12+1.5 = 13.5
Half of the diameter is the radius, so half of 13.5 = 6.75
Now, multiply pi (3.14) by the radius, but have the radius squared. You'd write the equation like this:
3.14 x 6.75^2 (or on paper, the ^2 would be a small two diagonal from the 5)
Actual answer: 143.06625
You can round that to 143.
Answer:
13
Step-by-step explanation:
25 - 12 = 13
You need to do 120-60=60 and that means he only needs $60.
Answer:
21:50
Step-by-step explanation:
We need to find the ratio of 420 m to 1 km.
We know that,
1 km = 1000 m
So,
The ratio becomes,
So, the required ratio is 21:50.
