College Algebra: Can anyone help me?? If $2500 is invested in the account that pays interest compounded continuously at a rate of 4%, how long will it take to double the investment? -- Formula: A=Pe^rt --Answer should be 17.3 years --HOW do I get the answer 17.3? Can someone show me? Solution P=2500 r=0.04 A = 2*2500 = 5000 2 = e^(0.04t).