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The station with the greatest average number of days of recorded snowfall during January of years 1961 through 2000 had the greatest total number of days with recorded snowfall during those years.: Might not be true
Cork had at least 2 days with recorded snowfall during February in each of the years from 1961 through 2000.: Might not be true
In at least one year from 1961 through 2000, the station at Valentia recorded 2 or more days of snowfall in a single calendar month.: Must be true
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
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Question Stats:
37% (03:04) correct
63%
(03:09)
wrong
based on 2250
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The table shows, for each of 10 Irish weather stations and each of 8 calendar months, the average (arithmetic mean) number of days per month that the station recorded snowfall during the years 1961–2000. For example, during this time period, the station at Birr recorded snowfall on an average of 4.5 days in January.
For each of the following statements about the weather stations listed in the table, select Must be true if that statement must be true if the information provided is correct. Otherwise, select Might not be true.
| Station | Jan | Feb | Mar | Apr | May | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|
| Belmullet | 4.6 | 4.3 | 3.5 | 1.7 | 0.2 | 0.0 | 0.7 | 2.7 |
| Birr | 4.5 | 3.3 | 2.5 | 1.0 | 0.2 | 0.0 | 0.5 | 2.5 |
| Claremorris | 6.5 | 5.3 | 4.5 | 1.9 | 0.2 | 0.1 | 1.6 | 3.6 |
| Clones | 6.2 | 5.8 | 4.4 | 1.8 | 0.4 | 0.1 | 1.6 | 3.8 |
| Cork | 3.9 | 4.1 | 2.6 | 1.1 | 0.1 | 0.0 | 0.5 | 2.4 |
| Dublin | 5.6 | 5.0 | 3.8 | 1.6 | 0.3 | 0.1 | 0.9 | 3.0 |
| Kilkenny | 4.5 | 4.3 | 2.7 | 0.9 | 0.1 | 0.0 | 0.5 | 2.4 |
| Mullingar | 6.0 | 5.3 | 3.9 | 2.0 | 0.2 | 0.0 | 1.0 | 3.5 |
| Rosslare | 2.3 | 3.1 | 1.6 | 0.7 | 0.1 | 0.0 | 0.2 | 1.1 |
| Valentina | 1.3 | 1.4 | 1.0 | 0.4 | 0.1 | 0.0 | 0.1 | 0.8 |
For each of the following statements about the weather stations listed in the table, select Must be true if that statement must be true if the information provided is correct. Otherwise, select Might not be true.
ID: 700220
| Must be true | Might not be true | |
| The station with the greatest average number of days of recorded snowfall during January of years 1961 through 2000 had the greatest total number of days with recorded snowfall during those years. | ||
| Cork had at least 2 days with recorded snowfall during February in each of the years from 1961 through 2000. | ||
| In at least one year from 1961 through 2000, the station at Valentia recorded 2 or more days of snowfall in a single calendar month. |
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Official Answer
The station with the greatest average number of days of recorded snowfall during January of years 1961 through 2000 had the greatest total number of days with recorded snowfall during those years.: Might not be true
Cork had at least 2 days with recorded snowfall during February in each of the years from 1961 through 2000.: Might not be true
In at least one year from 1961 through 2000, the station at Valentia recorded 2 or more days of snowfall in a single calendar month.: Must be true
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16 Mar 2024, 23:40
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1. The station with the greatest average number of days of recorded snowfall during January of years 1961 through 2000 had the greatest total number of days with recorded snowfall during those years.
Sort the table by Jan month. Claremorris has the greatest average number of days, which is 6.5
However, when you compare the averages every month of Claremorris with Clones, you can easily make it the averages are more for clones. We do not require to multiply number of days with the averages to get to the answer. The gap in the avergaes between the two stations cannot be covered by minor variations in days in months of a year.
Hence, 'Might not be true' is the answer.
2. Cork had at least 2 days with recorded snowfall during February in each of the years from 1961 through 2000.
The average over a month cannot tell us about the rains on the individual days.
Clearly, need not be true.
3. In at least one year from 1961 through 2000, the station at Valentia recorded 2 or more days of snowfall in a single calendar month.
Valentia had average rainfall of 1.3 and 1.4 in Jan and Feb. If rainfall was recorded on only one day each Feb every year, then the average would be 1 or less.
But 1.3 means, there were some years when the rains were there on at least 2 days.
Must be true
Sort the table by Jan month. Claremorris has the greatest average number of days, which is 6.5
However, when you compare the averages every month of Claremorris with Clones, you can easily make it the averages are more for clones. We do not require to multiply number of days with the averages to get to the answer. The gap in the avergaes between the two stations cannot be covered by minor variations in days in months of a year.
Hence, 'Might not be true' is the answer.
2. Cork had at least 2 days with recorded snowfall during February in each of the years from 1961 through 2000.
The average over a month cannot tell us about the rains on the individual days.
Clearly, need not be true.
3. In at least one year from 1961 through 2000, the station at Valentia recorded 2 or more days of snowfall in a single calendar month.
Valentia had average rainfall of 1.3 and 1.4 in Jan and Feb. If rainfall was recorded on only one day each Feb every year, then the average would be 1 or less.
But 1.3 means, there were some years when the rains were there on at least 2 days.
Must be true
Quote:
Video discussion on this question: https://youtu.be/Ucf5Q-IJbQ8
Some of the toughest DI questions are based on averages or weighted averages, as is this. Once you realise this and learn to navigate through it, the question becomes a whole lot easier and quicker.
The station with the greatest average number of days of recorded snowfall during January of years 1961 through 2000 had the greatest total number of days with recorded snowfall during those years.
Sort the table by Jan. Claremorris has maximum avg days of snowfall in Jan. But does it have maximum total number of days of rainfall too?
Coompare with Clones which is right above it - a possible candidate with fewer days of snow than Claremorris in some months and more days in other months.
Go month by month - Clones has 0.3 less in Jan, .5 more in Feb so 0.2 more till now. .1 less in March so .1 less till now. and so on.
We see that Clones has higher average number of days of snow. So Claremorris certainly is not the one with the highest total number of days of snow.
ANSWER: Might Not be True
Cork had at least 2 days with recorded snowfall during February in each of the years from 1961 through 2000.
Cork had on average 4.1 days of snow every year in Feb. But this is just the average. It is possible that in some years, it had no snow in Feb.
Hence, it is not necessary that it had at least 2 days with recorded snowfall during February in each of the years from 1961 through 2000.
ANSWER: Might Not be True
In at least one year from 1961 through 2000, the station at Valentia recorded 2 or more days of snowfall in a single calendar month.
Valentia recorded average of 1.3 days of snow in Jan. This means in some years, it would have recorded 2 or more days of snow. If that were not the case and in each year it had recorded only 0 or 1 day of snowfall in Jan, then the average could not have been 1.3.
Hence it is necessary that in at least one year from 1961 through 2000, the station at Valentia recorded 2 or more days of snowfall in a single calendar month.
ANSWER: Must be True
Here is a video discussing how to solve for average: https://youtu.be/W-qhIZ29UIs
Here is post that discusses the deviation concept: https://anaprep.com/arithmetic-usefulness-of-deviations/
