Formula for finding the area of a circle:

We need to radius but we only have the diameter.
Luckily for us, if you have the diameter, you have the radius.
Because the radius is the diameter over 2.
10 / 2 = 5
Plug in the values.
A = (3.14)5^2
A = (3.14)25
A = 78.5
So, the answer is 78.5.
Answer:
$4
Step-by-step explanation:
Total expenditure is $55
Breakdown
2 books cost $10
4 books cost $25
Subtotal for 6 books is 10+25=$35
Remaining amount from total is 55-35=$20
If each book costs approximately $5 then for $20, each book is 20/5=$4
Following PEDMAS it'd be
=0
0+(50x1)-60-(60x0)+10
0+50-60-0+10
50-60+10
-10+10=0
Hope this helps. :)