51,000
5 in the ten thousands,
The thousands value is 1, the hundreds is 4 (less than 5 so we round down)
In the real world you are not going to have a calculator on you 24/7. Nor will you have a pencil or paper to do longhand. You need to know how to accurately estimate your answers in order to be successful.
First, set the equation in exponential form.
x=logbY to b^x=Y
x=log44. so x=x, b=10, Y=44
10^x=44
I know that 10^1=10, 10^2=100, and 10^1.5=31.6 so x should be between 1.5 and 2.
The answer is x=1.64.