Explanation

Putting values is the best way to go about this problem. We know that the range of temperature is 20 in June and 25 in July

June		July
Lowest Daily	Highest Daily	Lowest Daily	Highest Daily
5	25	0	25

So the range in 2 month period = 25 -5 = 20. So quantity B is greater.

Now choosing another set of values

June		July
Lowest Daily	Highest Daily	Lowest Daily	Highest Daily
5	25	35	60

So the range in 2 month period = 60 -5 = 55. So quantity A is greater.

Clearly D is the correct option.
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GIVEN: In City X, the range of the daily low temperatures during June 2012 was 20° Fahrenheit, and the range of the daily low temperatures during July 2012 was 25° Fahrenheit.

There are infinitely-many scenarios that satisfy the above conditions. Here are two possible cases:

case i
June: 0°, 0°, 0°, 0°, 0°, 0°, 0°, 0°, .....0°, 0°, 0°, 0°, 20° (range = 20°)
July: 0°, 0°, 0°, 0°, 0°, 0°, 0°, 0°, .....0°, 0°, 0°, 0°, 25° (range = 25°)
June and July combined: 0°, 0°, 0°, 0°, 0°, 0°, 0°, 0°, .....0°, 0°, 0°, 0°, 20°, 25° (range = 25°)

We get:
QUANTITY A: 25°
QUANTITY B: 30°
In this case, Quantity B is greater
---------------------------

case ii
June: 0°, 0°, 0°, 0°, 0°, 0°, 0°, 0°, .....0°, 0°, 0°, 0°, 20° (range = 20°)
July: 10°, 10°, 10°, 10°, 10°, 10°, 10°, 10°, .....10°, 10°, 10°, 10°, 35° (range = 25°)
June and July combined: 0°, 0°, 0°, 0°, 0°, .... 0°, 0°, 10°, 10°, 10°...., 10°, 10°, 20°, 35° (range = 35°)

We get:
QUANTITY A: 35°
QUANTITY B: 30°
In this case, Quantity A is greater

Answer: D

Cheers,
Brent
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