Question 1031079
{{{d(n)= (0.75)sqrt( 2.8n)}}}
We want to know n when d(n) = 81
{{{81 = (0.75)sqrt( 2.8n)}}}
divide each side by 0.5
{{{81/0.75 = sqrt( 2.8n)}}}
{{{108 = sqrt( 2.8n)}}}
square both sides
{{{108^2 = 2.8n}}}
divide each side by 2.8
{{{108^2/2.8 = n}}}
{{{4165.714 = n}}} approximately