Question 1192941
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You make a lot of extra unnecessary work by immediately taking logs of both sides, as the other tutor did.  Make the work MUCH easier by first dividing both sides by 400.<br>
{{{200=400e^(-0.0052x)}}}
{{{e^(-0.0052x)=0.5}}}<br>
NOW take logs of both sides<br>
{{{-0.0052x=ln(0.5)}}}
{{{x=ln(0.5)/-0.0052}}} = 133.30 to 2 decimal places<br>
ANSWER: 133.30<br>