Learn how to rewrite any logarithm using logarithms with a different base. This is very useful for finding logarithms in the calculator!
Log in Sara Harper 7 years agoPosted 7 years ago. Direct link to Sara Harper's post “This question is about th...” This question is about the 3rd practice example on this page. When I put the equation into my calculator, it came up with -0.868483 (ect). So I rounded the 4 up to a 5 since the number to the right of it was 8, and in turn, rounded up the 8 to a 9, to come up with -0.869. But when I put that in as my answer, Khan said I was incorrect. As soon as I changed the answer to -0.868, however, I was told it was correct. Isn't that inaccurate? • (9 votes) kubleeka 7 years agoPosted 7 years ago. Direct link to kubleeka's post “"To the nearest thousandt...” "To the nearest thousandth" means to three digits right of the decimal. You cannot round something by first rounding to other decimal places. For example, say we're told to round 45 to the nearest hundred. If we do what you did here, we first round to 50, then round 50 up to 100. But 45 is closer to 0 than to 100, so this is inaccurate. We need to just round down to 0 in the first place. (60 votes) Tapiwa Hellcat 5 years agoPosted 5 years ago. Direct link to Tapiwa Hellcat's post “How is log(50)/log(2) equ...” How is log(50)/log(2) equal to ln(50)/ln(2)? Since the power to which base (10) is raised to give us 50 is not the same power to which base (e) is raised to give us 50. Same goes for log(2) and ln(2). • (8 votes) kubleeka 5 years agoPosted 5 years ago. Direct link to kubleeka's post “You're correct that log(5...” You're correct that log(50)≠ln(50) and log(2)≠ln(2). That doesn't mean that their ratios cannot be the same, for the same reason that 2≠4 and 3≠6 doesn't mean that 2/3≠4/6. Say log(50)/log(2)=x. Then log(50)=xlog(2) FeatherwishWC 4 months agoPosted 4 months ago. Direct link to FeatherwishWC's post “If you're reading this, I...” If you're reading this, I just want to let you know these things are really tricky to master. If you're having trouble understanding it, it's okay! You're doing a great job pushing through and sticking with this. Keep going and have a great day :) • (17 votes) FeatherwishWC a month agoPosted a month ago. Direct link to FeatherwishWC's post “If you're having a bad da...” If you're having a bad day, let me know and I'll do my best to help you with whatever's going on. Please don't worry - everything will be okay, somehow, someday. Push through - you don't know what you can do, what you've still got left in you. And when all is said and done, just remember this one thing: You can do it. (2 votes) travisk21 4 years agoPosted 4 years ago. Direct link to travisk21's post “what if there is a number...” what if there is a number in front of LOG • (5 votes) Hecretary Bird 4 years agoPosted 4 years ago. Direct link to Hecretary Bird's post “If there is a number in f...” If there is a number in front of the log symbol, it is a coefficient. When you see the expression a*log_b(c), you would first find the log base b of c, and then multiply the result by a. Hope this helps. (13 votes) ks a year agoPosted a year ago. Direct link to ks's post “Why can't we just plug in...” Why can't we just plug in the logs on a calculator, (on a TI-84 you can calculate logs with other bases) you can just do for example if you wanted log₂(8) you can just do log(8, 2) on the calculator and it outputs 3. Kim Seidel a year agoPosted a year ago. Direct link to Kim Seidel's post “Many calculators (less ex...” Many calculators (less expensive than a TI-84) only have ln or log base 10. The change of base rule enables you to use these calculators to get the result. (7 votes) Alessandro V. Santoro a year agoPosted a year ago. Direct link to Alessandro V. Santoro's post “Hello, everyone.Maybe a...” Hello, everyone. Maybe a silly question, but I don't remember previously hearing about it (or I forgot): why can't the argument be negative? Is it a rule for all logarithms or only for the rule to hold? Thanks in advance • (8 votes) kubleeka a year agoPosted a year ago. Direct link to kubleeka's post “log(a) is the power to wh...” log(a) is the power to which you must raise 10 in order to get a. But raising 10 to any power yields a positive number. Specifically, there is no real number x such that 10^x is negative. So logarithms of negative numbers don't exist in the real numbers. (You can make logarithms of negatives work using imaginary/complex numbers, but it's a complicated matter, beyond K-12 use of complex numbers.) (7 votes) George Lithoxopoulos 10 months agoPosted 10 months ago. Direct link to George Lithoxopoulos's post “to solve the challenge pr...” to solve the challenge problem it is possible by setting log(81)/log(3) to x.... then solve for x and by using the exponent rule in reverse you get x=4 • (7 votes) Kim Seidel 10 months agoPosted 10 months ago. Direct link to Kim Seidel's post “You can use the change of...” You can use the change of base rule in revers to convert log(81)/log(3) into log3(81). Then find the exponent that when applied to 3 = 81, which is 4. (4 votes) mary.kopchick 7 years agoPosted 7 years ago. Direct link to mary.kopchick's post “Is log equivalent to a n...” Is log equivalent to a numerical value (like pi) ? • (2 votes) Matthew Johnson 7 years agoPosted 7 years ago. Direct link to Matthew Johnson's post “`A logarithm is a functio...” (11 votes) CalebXtreme 5 months agoPosted 5 months ago. Direct link to CalebXtreme's post “logarithms just got hard” logarithms just got hard • (6 votes) Jafrin Rosary 6 years agoPosted 6 years ago. Direct link to Jafrin Rosary's post “What can I do during an e...” What can I do during an exam? I CAN'T USE A CALCULATOR! HELP! The theory was very useful though. :-) • (5 votes) Diarasis Rodriguez 6 years agoPosted 6 years ago. Direct link to Diarasis Rodriguez's post “See the _[I need help!]_ ...” See the [I need help!] right below Challenge Problem 1. (3 votes)Want to join the conversation?
3) Evaluate log_4(0.3)
Round your answer to the nearest thousandth.
log(50)=log(2^x) by logarithm properties
50=2^x, raising both sides to the 10th power. Do you see how we end up with this same equation regardless of the base of the logarithms?
If so, why does the rule require this?A logarithm is a function. This means it will operate on a set of numbers using a set of rules. π is a constant number. This means it has a fixed, unchanging (but ever growing) value (it is a real number, in spite of the infinite digits)
