The series, a1, a2, a3, ... is defined such that each term after the first is twice the previous one. If a5 - a2 = 12, what is the value of a1?
a) 4
b) 24/7
c) 2
d) 12/7
e) 6/7
a) 4
b) 24/7
c) 2
d) 12/7
e) 6/7
a2 = 2(a1),rnaah wrote:The series, a1, a2, a3, ... is defined such that each term after the first is twice the previous one. If a5 - a2 = 12, what is the value of a1?
a) 4
b) 24/7
c) 2
d) 12/7
e) 6/7
a3 = 2(a2) = 4(a1),
a4 = 2(a3) = 8(a1),
a5 = 2(a4) = 16(a1)
Now, a5 - a2 = 12 implies 16(a1) - 2(a1) = 12 or 14(a1) = 12
So, a1 = 12/14 or 6/7
The correct answer is E.
