The equation of a circle:

(h, k) - a coordinates of the center
r - a radius
A diameter d = 2r
We have

Answer: d = 2 · 10 = 20
Answer:
rs 38.
Step-by-step explanation:
Total cost of the 80 books = 80*30 = rs 2400.
He had 60 books to sell and made a 5% loss.
Thus his income from these books was 2400 - 0.05*2400 = rs 2280.
So the selling price of each book was 2280 / 60 = rs 38.
Answer:
see below
Step-by-step explanation:
A. 3.75 * 10 = 37.5
B. 3.75 - 10 = -6.25
C. 2.5 - 10 = -7.5
D. 2.5 + 100 = 102.5
E. 8.75 + 10 = 18.75