Question

Difficulty: EasyLogarithms and Change of Base

What is the value of log316×log227\log_3 16 \times \log_2 27?

  1. 1212Answer
  2. B
    77
  3. C
    432432
  4. D
    66

Answer

The value of log316×log227\log_3 16 \times \log_2 27 is 1212.
By applying the power law of logarithms, log316=4log32\log_3 16 = 4\log_3 2 and log227=3log23\log_2 27 = 3\log_2 3. Multiplying these gives (4×3)(log32×log23)(4 \times 3)(\log_3 2 \times \log_2 3). Using the change of base identity log32×log23=1\log_3 2 \times \log_2 3 = 1, the product simplifies to 1212.

Step-by-Step Solution

1
Rewrite 1616 and 2727 as prime powers
log316=log3(24)\log_3 16 = \log_3 (2^4) and log227=log2(33)\log_2 27 = \log_2 (3^3)
Express numbers in terms of base prime factors to simplify logarithmic powers.
2
Apply the power law of logarithms logb(ak)=klogba\log_b (a^k) = k \log_b a
log3(24)=4log32\log_3 (2^4) = 4 \log_3 2 and log2(33)=3log23\log_2 (3^3) = 3 \log_2 3
Bring the exponents out as multipliers.
3
Multiply the expressions and apply the change of base reciprocal property logab×logba=1\log_a b \times \log_b a = 1
(4log32)×(3log23)=12×(log32×log23)=12×1=12(4 \log_3 2) \times (3 \log_2 3) = 12 \times (\log_3 2 \times \log_2 3) = 12 \times 1 = 12
The logarithmic terms are reciprocals of each other, simplifying their product to 1.

Key Concept

Change of Base and Power Laws of Logarithms
Estimated Time:45s
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