Arithmetic Aptitude :: Problems on Numbers
7. In a group of donkeys and pigs, the numbers of legs are 16 more than twice the number of heads. The number of donkeys is
Let the number of donkeys be x and the number of pigs be y.
=> 4x + 2y = 2(x + y) = 16.
=> 2x + (2x + 2y) = (2x + 2y) + 16.
=> x = 8.