Find Log₂18 . We know that 2⁴ = 16 and 2⁵ = 32 , and that 18 is between 16 and 32; therefore, we know that the exponent we are looking for is between 4 and 5. In fact, it is closer to 4 than to 5 because 18 is closer to 16 than it is to 32.

Plz Check....

Let's solve this problem by changing the base to 10. Log₂18 can be written   Log18 / Log2 . Using your calculator,

                    Log18 / Log2  =  1.255273/0.301030 = 4.169927.

Let's check the answer. If  2 ^4.169927  = 18  , our answer is correct.2 ^4.169927  = 18.000025 . Close enough. Why isn't it 18 exactly?

Since we rounded Log18 / Log2 to six places, our answer won't check exactly. If we rounded to ten places, then when we checked the answer, it would be closer to 18 than this answer.