Question

In preparation for Halloween, three married couples, the Browns, the Joneses and the Smiths, brought little presents for the neighborhood children. Each bought as many identical presents as he (she) paid cents for one of them. Each wife paid 75 cents more the her husband, Ann bought one more present than Bill Brown, Betty one less present than Joe Jones. What is Mary’s last name?

Hint:   (x + y)(x – y) = 75

Answer 1

( x+ y) ( x- y) = 75

x + y = 75

x - y = 1

solving the equation we get

x = 38 , y = 37

2nd condition

x + y = 25

x - y = 3

solving we get

x = 14 , y = 11

3rd condition

x + y = 15

x - y = 5

solving we get

x = 10 , y = 5

from solution 1 , x = 38 and y = 37

the difference is 1 , which means Ann is the wife of Bill brown

as Ann bought one more present than Bill Brown

and Betty is not the wife of Joe jones as we did not get any condition on this

hence, Marys last name could be "Jones "