How many female fighters who were in the 20 to less than 30 coin bracket in 1980 retired between the 2010 and 2020 observations?
Refer to the bar graph provided with this set.
Refer to the bar graph provided with this set.
Answer and solution
Correct answer: 40
Solution
Answer: 40
1. Track the same cohort over time, rather than comparing one fixed coin bracket.
2. A female fighter in bracket 20–30 in 1980 is in bracket 50–60 in 2010 and 60–70 in 2020.
3. The graph gives 145 active female fighters for the first observation and 105 for the second.
4. Retirements between the observations=145−105=40. The value 30 belongs to 2000–2010 and is not the interval now asked.
Detailed setup and verification:
Draw a four-decade chain for this female cohort:20–30 in 1980,30–40 in 1990,40–50 in 2000,50–60 in 2010 and 60–70 in 2020. The relevant 2010 and 2020 bars are purple-light and pale orange, respectively.
A cohort is a fixed group: its fall from 145 active fighters to 105 means 40 retirements during that interval. The percentage retired would be 40/145, but the question asks for a number, so no division or percent sign belongs in the answer.
Verification: 4. Retirements between the observations=145−105=40. The value 30 belongs to 2000–2010 and is not the interval now asked.
Trap to avoid: Use the exact requested cohort, statistic or rank condition; the worked check above establishes the result.
1. Track the same cohort over time, rather than comparing one fixed coin bracket.
2. A female fighter in bracket 20–30 in 1980 is in bracket 50–60 in 2010 and 60–70 in 2020.
3. The graph gives 145 active female fighters for the first observation and 105 for the second.
4. Retirements between the observations=145−105=40. The value 30 belongs to 2000–2010 and is not the interval now asked.
Detailed setup and verification:
Draw a four-decade chain for this female cohort:20–30 in 1980,30–40 in 1990,40–50 in 2000,50–60 in 2010 and 60–70 in 2020. The relevant 2010 and 2020 bars are purple-light and pale orange, respectively.
A cohort is a fixed group: its fall from 145 active fighters to 105 means 40 retirements during that interval. The percentage retired would be 40/145, but the question asks for a number, so no division or percent sign belongs in the answer.
G Strategy shortcut
Method: Follow the cohort diagonally: 1980 bracket 20–30 →2010 bracket 50–60 →2020 bracket 60–70. Subtract 145−105=40.Verification: 4. Retirements between the observations=145−105=40. The value 30 belongs to 2000–2010 and is not the interval now asked.
Trap to avoid: Use the exact requested cohort, statistic or rank condition; the worked check above establishes the result.
G Strategy: Method: Follow the cohort diagonally: 1980 bracket 20–30 →2010 bracket 50–60 →2020 bracket 60–70. Subtract 145−105=40. Verification: 4. Retirements between the observations=145−105=40. The value 30 belongs to 2000–2010 and is not the interval now asked. Trap to avoid: Use the exact requested cohort, statistic or rank condition; the worked check above establishes the result.