Problem: The area of a circle is doubled when its radius r is increased by n. Then r equals:
Answer Choices:
A. n(2β+1)
B. n(2ββ1)
C. n
D. n(2β2β)
E. 2β+1nΟβ
Solution:
A=Οr2
2A=Ο(r+n)2
2Οr2=Ο(r2+2rn+n2)
r=n(1+2β); the value 1β2β is not used