Answer:
It will take 47 months ( 3 years and 11 months)
Explanation:
We use the compound interest formula here.
Mathematically;
A = P( 1 + r)^t
Where A is the amount which is 2 times the principal here, so we can call it 2P
P is the lump-sum invested
r is the monthly interest rate given as 1.5% = 1.5/100 = 0.015
t = time , which we want to calculate
Substituting these values, we have;
2P = P(1 + 0.015)^t
divide both sides by P
2 = 1.015^t
Take the log of both sides;
log 2 = log (1.015)^t
log 2 = t log 1.015
t = log2/log1.015
t = 46.55
which is approximately 47 months