the sum of the squares of 3 numbers is 241 , while the sum of their products taken two at a time is 100 . their sum is :  Pick:	A) 20	B) 11	C) 21	D) 41	E) none of these

Rationale: x ^ + y ^ 2 + z ^ 2 = 241 xy + yz + zx = 100 as we know . . ( x + y + z ) ^ 2 = x ^ 2 + y ^ 2 + z ^ 2 + 2 ( xy + yz + zx ) so ( x + y + z ) ^ 2 = 241 + ( 2 * 100 ) ( x + y + z ) ^ 2 = 441 so x + y + z = 21 answer : c
Answer: C