Force of interest problem

[Ronan1990]

Nope. Did you take the natural log first? The interest rate is increasing over time, not decreasing.

I get m = .01 and b = .07

It's easy to drop a step in force of interest problems. You'll often get an answer that isn't obviously wrong. That answer is also sometimes one of the other multiple-choice answers.

I must be forgetting basic maths or something because when i get to here:

ln(1.03691504) = .125 m + .5 b
ln(1.05687083) = .28125 m + .75 b


0.03624999725 = .125 m + .5 b
0.05531249507 = .28125 m + .75b

and when i solve for the values of b & m I end up with them ridiculous long decimal numbers as opposed to 0.1 & 0.7

[Kenneth]

I must be forgetting basic maths or something because when i get to here:

ln(1.03691504) = .125 m + .5 b
ln(1.05687083) = .28125 m + .75 b


0.03624999725 = .125 m + .5 b
0.05531249507 = .28125 m + .75b

and when i solve for the values of b & m I end up with them ridiculous long decimal numbers as opposed to 0.1 & 0.7

Show me your steps.

[Ronan1990]

Show me your steps.

0.125m + 0.5b = 0.03624999725 (ln(1.03691504))
0.28125m + 0.75b = 0.05531249507

so simultaneous equations, multiply the top line by -1.5 to get

-0.1875m -0.75b = -0.05437499588
0.28125m +0.75b = 0.05531249507

which cancels to some really long decimal value for m so I must be doing my simultaneous equations wrong

[Kenneth]

0.125m + 0.5b = 0.03624999725 (ln(1.03691504))
0.28125m + 0.75b = 0.05531249507

so simultaneous equations, multiply the top line by -1.5 to get

-0.1875m -0.75b = -0.05437499588
0.28125m +0.75b = 0.05531249507

which cancels to some really long decimal value for m so I must be doing my simultaneous equations wrong

-0.1875m -0.75b = -0.05437499588
0.28125m +0.75b = 0.05531249507

adding them up:

.09375m = .00093749919

dividing by the whole number in front of the m (including the sign), I get:

m = .00999999136

I feel safe in rounding this to .01

When I ask for steps, I'm not asking for step 1 of 6, I'm asking for all 6 steps.