The graph shows the total energy usage in kilowatt hours (kWh) for

It should be 300kWh. Rounding off to the nearest 50kWh should be redundant in this case, since the greatest quarterly median reaches approximately 975 kWh, the lowest reaches around 675kWh, and that gives a difference of 300kWh, with zeroes in the tens' or units' digits.

The graph shows the total energy usage in kilowatt hours (kWh) for a small retail business for each month of last year. The business owner is interested in comparing the business's median monthly energy usage per quarter among Quarter 1 (January through March), Quarter 2 (April through June), Quarter 3 (July through September), and Quarter 4 (October through December).

The business's median monthly energy usage for  Quarter 1 (January through March) = 730 KWH
The business's median monthly energy usage for  Quarter 2 (April through June) = 790 KWH
The business's median monthly energy usage for  Quarter 3 (July through September) = 950 KWH
The business's median monthly energy usage for  Quarter 4 (October through December) = 700 KWH

Select from the drop-down menus the options that create the sentence that most accurately reflects the information provided.

Among the quarterly medians (the medians of the business's monthly energy usages for each quarter), the greatest quarterly median was for Quarter 3, and that quarterly median exceeded the least quarterly median by 950-700=250 kWh, to the nearest 50 kWh.­

­Well spotted. Thanks for the explanation.

for 2nd part of the question, the difference is 950 minus something slightly smaller than 700(like 695, 699 etc)
= 950 - <700
= something slightly greater than 250
= rounded to nearest 50 it will give 250 and not 300.

Rounding logic:
If a number rounds to 250 when rounded to the nearest 50, the possible range includes all numbers that are closer to 250 than to the neighboring multiples of 50 (i.e., 200 and 300).

Calculation:
Halfway between 200 and 250: 225
Halfway between 250 and 300: 275
Range:
Any number from 225 to 274 will round to 250 when rounded to the nearest 50.
Final range: 225 ≤ number < 275.