Bunuel wrote:
Yesterday Wanda prepared several shipments of lightbulbs and several shipments of electrical cords. How many minutes did Wanda spend preparing the shipments of lightbulbs yesterday?
(1) Yesterday the average (arithmetic mean) number of minutes that Wanda spent per shipment of lightbulbs was 20 percent greater than the average number of minutes that she spent per shipment of electrical cords.
(2) Yesterday Wanda spent a total of 90 minutes preparing all of the shipments.
We need to answer the question:
total lightbulbs time = ?
Statement One Alone:=> Yesterday the average (arithmetic mean) number of minutes that Wanda spent per shipment of lightbulbs was 20 percent greater than the average number of minutes that she spent per shipment of electrical cords.
If the average electrical cords time is “e,” then the average lightbulbs time is “1.2e.”
Since no information is given about actual time lengths in minutes, etc., we can’t answer the question.
Statement one is not sufficient. Eliminate answer choices A and D.
Statement Two Alone:=> Yesterday Wand spent a total of 90 minutes preparing all of the shipments.
Although we know the total time, we don’t know the ratio of total lightbulbs time to total electrical cords time.
Statement two is not sufficient. Eliminate answer choice B.
Statements One and Two Together:If the number of lightbulbs shipments prepared is “L,” and the number of electrical cords shipments prepared is “E,” then we have:
total lightbulbs time + total electrical cords time = 90 minutes
(1.2e)L + (e)E = 90
We still don’t know the ratio of total lightbulbs time to total electrical cords time, because we have:
(1.2e)L/[(e)E] = 1.2L/E
The two statements together are not sufficient.
Answer: E