The value of an “Aerosoul” stock

The value of an “Aerosoul” stock changes according to the following method:
At the end of each month her value is doubled but due to commission the stock’s value is decreases by $10. If the value at the beginning of January is $A, what would be her value at the end of February?
(a) 4A – 10.
(b) 4A – 20.
(c) 4A – 30.
(d) 4A – 40.
(e) 4A – 50 .

The best answer is C.
At the end of January her value is 2A – 10.
At the end of February her value is (2 x (2A – 10) – 10 = 4A – 30).



An Ameba is an organic life form that divides into two Amebas each round hour. If at a certain round hour, two Amebas were placed in a jar, how many Amebas will be in the jar in N hours?

(a) 2N
(b) 22N
(c) 2N+1
(d) 2N-1
(e) 2N

The best answer is C.
Let’s find the number of Amebas in the first hours.
After one hour (N=1) there will be 4 Amebas.
After two hours (N=2) there will be 8 Amebas.
After three hours (N=3) there will be 16 amebas.
Therefore the formula that fits this series is 2N+1.