Question 14639
<pre>
5* = 100

* log 5 = log 100

* = log 100/log 5

* = 2/log 5


another method is to use trial and error

*          5*                 comment
1          5                  too small
3          125                too big
2          25                 too small
2.5        55.9               too small
2.7        77.13              too small
2.9        106                too big
2.85       98.2               too small
2.87       101.82             too big

ans approx = 2.86</pre>