AAPL wrote:Economist GMAT
Mona and Donald fly to Rome for the weekend. They take cash only in notes of $10 and notes of €10. Mona carries three times the amount of euros Donald carries. She also carries as many dollars as Donald carries. The number of €10 notes they take is double the number of $10 notes they take. If Donald carries a total of 40 notes (of either $10 or €10) then what is the total number of notes (of either $10 or €10) they take?
A. 70
B. 80
C. 100
D. 120
E. 150
We can PLUG IN THE ANSWERS, which represent the total number of notes.
The number of €10 notes they take is double the number of $10 notes they take.
Thus, the ratio of €10 notes to $10 notes = 2:1.
Since the sum of the parts of this ratio = 2+1 = 3, the total number of notes must be a MULTIPLE OF 3.
Eliminate A, B and C.
D: 120 notes
Here, the total number of notes (120) is 40 times as great as the sum of the parts of the ratio above (2+1=3), implying that the two values in the ratio must each be multiplied by 40:
€10 notes = 2*40 = €80.
$10 notes = 1*40 = $40.
Mona carries as many dollars as Donald carries.
Since they have a total of $40, Mona = $20 and Donald = $20.
Donald carries a total of 40 notes.
Since Donald has $20,
he must have €20, for a total of 40 notes.
Since they have a total of €80, and Donald has €20,
Mona must have €60.
Only one condition remains:
Mona carries three times the amount of euros Donald carries.
Success!
According to the green portions above, Mona's amount in Euros (€60) is 3 times Donald's amount in Euros (€20).
The correct answer is
D.
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