Question 61332
As I understand it the problem is 
{{{4sqrt(10) * 7sqrt(15)}}} 
The square root of ten is the same as the square root of 2 multiplied by the square root of 5. 
The square root of 15 is the same as the square root of 3 multiplied by the square root of 5.
So the problem could be rewritten as
{{{4sqrt(2)*sqrt(5) * 7sqrt(3)*sqrt(5)}}} {{{sqrt(5)*sqrt(5)=5}}}
{{{4*7*sqrt(5)*sqrt(5)*sqrt(2)*sqrt(3)}}}
{{{28*5*sqrt(2)*sqrt(3)}}}
{{{140*sqrt(2)*sqrt(3)}}}and {{{sqrt(2)*sqrt(3)=sqrt(6)}}} so
{{{140sqrt(6)}}}