Bunuel
If Susan has $5 more than Tom, and if Tom has $2 more than Ed, which of the following exchanges will ensure that each of the three has an equal amount of money?
(A) Susan must give Ed $3 and Tom $1.
(B) Tom must give Susan $4 and Susan must give Ed $5.
(C) Ed must give Susan $1 and Susan must give Tom $1.
(D) Susan must give Ed $4 and Tom must give Ed $5.
(E) Either Susan or Ed must give Tom $7.
We can let S, T and E be the amount of money Susan, Tom and Ed have, respectively. We can create the equations:
S = T + 5
and
T = E + 2
Thus S = E + 2 + 5 = E + 7 and the sum of the three people, in terms of E, is E + 7 + E + 2 + E = 3E + 9. Thus if each have an equal amount of money, each will have E + 3. Now, let’s look at the options.
(A) Susan must give Ed $3 and Tom $1.
If Susan gives Ed $3 and Tom $1, she will have E + 7 - 3 - 1 = E + 3, Ed will have E + 3 and Tom will have E + 2 + 1 = E + 3. So each does have equal amount of money if Susan gives Ed $3 and Tom $1.
Alternate Solution:
Let’s assume that, at the start of the problem, Ed has $5, Tom has $7, and Susan has $12. The total amount of money is, therefore, 5 + 7 + 12 = 24. Each person needs to have the same amount of money, which is 24/3 = $8. Thus, Susan must give $3 to Ed and $1 to Tom.
Answer: A