GMAT Club Official Solution:A warehouse manager recorded the weights of all the crates in one shipment. How many crates were in the shipment?(1) The average (arithmetic mean) weight and the median weight of the crates in the shipment were both 18 kilograms.
This does not determine the number of crates.
For example, the shipment could have 1 crate weighing 18 kilograms.
Or the shipment could have 3 crates weighing 12, 18, and 24 kilograms. The average and median are both 18 kilograms.
Not sufficient.
(2) In the shipment, one crate weighed more than 18 kilograms, and one crate weighed less than 18 kilograms.
This does not determine the number of crates. It only tells us that there must be at least 2 crates.
Not sufficient.
(1)+(2) Even together, the statements do not determine the number of crates.
For example, the crate weights could be:
16, 18, 20
The average is 18, the median is 18, one crate weighs more than 18, and one crate weighs less than 18. There are 3 crates.
But the crate weights could also be:
16, 18, 18, 18, 20
The average is 18, the median is 18, one crate weighs more than 18, and one crate weighs less than 18. There are 5 crates.
Not sufficient.
Answer: E.