Answers

2014-03-07T16:10:25+05:30
No easy ways, just memorize them
0
2014-03-07T16:57:43+05:30
You can find easily by breaking it into smaller numbers.As if you had to find square-root of 20 -
 =√20
 =√2×2×5 
 = 2√5    (if one pair is available make it out the root)

you can also use this method in cube roots

1 5 1