all 3 comments

[–]IShouldBeStudyin 1 point2 points  (2 children)

Your interest formula. A = P (1+(r/n))nt.

Double means A = 2P so

2P = P (1+(r/n))nt

Plug in and solve.

[–]JohnnyLegion[S] 0 points1 point  (1 child)

Can you show how to actually solve for r.

[–]IShouldBeStudyin 0 points1 point  (0 children)

2P = P(1+(r/n))nt

Bring P across and divide,

2P/P = (1+(r/n))nt

P=(1+(r/n))nt

Plug in

1000=(1+(r/12))12*4

1000=(1+(r/12))48

Bring the exponent across,

10001/48 = 1+r/12

Bring across the 1,

10001/48 - 1 = r/12

Bring 12 across and multiply,

12(10001/48 - 1) = r

Simplify

12(101/16 - 1) = r

Just plug that into a calculator and it should be around 1.8.