Law of Logs
Evaluate (No Calculator)
Expand the Log
Combine Into One Log
Change of Base and Application
100

This law says when you multiply inside a log, you add the logs.

What is the product rule?

100

log(50) + log(200)

What is log(10,000) = 4?

100

log₃(5x²)

What is log₃5 + 2log₃x?

100

log x + log y

What is log(xy)?

100

Write log₂3 using natural logs.

What is ln(3)/ln(2)?

200

This law says when you divide inside a log, you subtract the logs.

What is the Quotient Rule?

200

log₄(960) − log₄(60)

What is log₄(16) = 2?

200

ln(2xy)

What is ln2 + lnx + lny?

200

log x − log y

What is log(x/y)?

200

Write log₁₅(4784) using common logs.

What is log(4784)/log(15)?

300

This law allows you to bring an exponent in front of a log.

What is the Power Rule?

300

log₂(8³⁵)

What is 35·log₂(8) = 35·3 = 105?

300

log₅( (5x²)/√y )

What is log₅5 + 2log₅x − (1/2)log₅y?

300

3log₂5 + (1/2)log₂7

What is log₂(5³√7)?

300

Why do we use change of base?

What is because calculators only compute log (base 10) and ln (base e)?

400

This is the base used in natural logarithms (ln).

What is e?

400

log₂6 − log₂15 + log₂20

What is log₂( (6·20)/15 ) = log₂(8) = 3?

400

log(√ab)

What is (1/2)(log a + log b)?

400

logb(x2-1)-logb(x-1)

What is logb(x + 1)?


400

In Ebbinghaus’ Law, what does “t” represent?

What is time in months?

500

This rule converts logs from one base to another using division.

What is the Change-of-Base Formula?

500

log₅(25)

What is 2?

500

log(x³y²/z)

What is 3logx + 2logy − logz?

500

log x + log(x² − 49) − log 5 − log(x + 9)

What is log( (x(x−7)) / 5 )?

500

If log(P) = log(87) − 0.3log(25), solve conceptually: does P increase or decrease over time?

What is decrease?