reto wrote:
#p is defined as 2p-20 for any number p. What is p, if #(#(#p))=4?
A. –108
B. –44
C. 10
D. 16
E. 18
How do you guys solve such questions other than with Plugging In the AC? I am curious to know your preffered approach. Thanks. It took me 3 minutes 17 seconds with plugging in.
Should be straightforward even without plugging in.
Lets use algebra for this:
#p = 2p-20 --->#(#p) = 2(2p-20)-20 = 4p-60 and thus #(4p-60) = 2(4p-60)-20 = 8p-140 = 4 ---> 8p= 144 ---> p = 16, D is the correct answer. Close to 1.5 minutes. Although this is more straightforward approach, you just need to be careful with your algebra all throughout.