Math help
posted by josiah .
how many years will it take for $4,000 to double at a simple intrest of 5%

the answer is 40 years. Hope this helps

annual interest = .05(4000) = 200
to double, we need another $4000
number of years = 4000/200 = 20
it will take 20 years
check:
simple interest on $4000 for 20 years at 5%
= .05(20)(4000) = 4000
so amount = what we had + new amount
= 4000 + 4000 = 8000 which is double what we started with
The answer of 40 years in not correct.
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