Log Equations help please!

1. A mammal's resting metabloic rate (R), in kilocalories per day, is related to its mass, m, in kilograms, by the equation

logR=log73.3 +0.75 log m. Predict the mass of a wolf with a resting metabloic rate of 1050 Kcal/day

2. Mahal invests $500 in an account with an annual percentage rate of 5% compounded quartely. How long will it take for Mahal's single investment to double in value?

b) Mahal invests $500 at the end of every 3 months in an accountant with an annual percentage rate of 4.8% compounded quarterly. How long will it take for Mahal's investment to be worth 100,000? Use FV= R[(1+i)^n-1] / i

where FV= future value, n is the number of equal periodic payments of R dollars, and i is the interest rate per compounding period expressed as a decimal

Please any help

Re: Log Equations help please!

1.) You want to solve the equation:

$\displaystyle \log(R)=\log(73.3)+0.75\log(m)$

for $\displaystyle m$.

Have you any thoughts on what steps you should take to do this?

Re: Log Equations help please!

i tried subtracting log(73.3) then divide by .75 didnt, then second log didnt work or maybe i made a calculator error if that is correct

Re: Log Equations help please!

Yes, those are good first steps which gives you:

$\displaystyle \log(m)=\frac{4}{3}\left(\log(R)-\log(73.3) \right)$

Now, is there a property of logs that will allow us to combine the two log terms on the right?

Re: Log Equations help please!

(4/3) (logR / log(73.3)) = log m ?

Re: Log Equations help please!

oh i got it, i cant seem to get the interest ones though

Re: Log Equations help please!

You are not properly using the logarithmic property you want, the property you want to use is:

$\displaystyle \log_a(b)-\log_a(c)=\log_a\left(\frac{b}{c} \right)$

Can you use this to rewrite the equation?

Re: Log Equations help please!

Not quite, but you are close. You should end up with a single log term on each side.