Refer to the bar graph provided with this set.
Answer and solution
Correct answer: D
Solution
1. The starting cohorts below 30 are 10–20 and 20–30 in 1980.
2. Forty years add 40 coins, moving these cohorts to 50–60 and 60–70 in 2020.
3. Read the orange and pale-orange bars, not the other year colours: 50–60 has 140 males and 100 females; 60–70 has 125 males and 105 females.
4. Add both genders across both cohorts: 140+100+125+105=470.
5. Answer: D, 470.
6. Track a cohort diagonally through the chart: add 10 to its bracket for each decade, rather than comparing the same bracket across years.
Detailed setup and verification:
The phrase less than 30 refers to the starting year 1980. There were two eligible brackets, each with 250 members of each gender. Move those same cohorts forward 40 years before reading the graph. The labels 50–60 and 60–70 in 2020 identify them; the chart’s youngest brackets do not.
As a cross-check, male survivors in the two target brackets total 265 and female survivors total 205. Their combined 470 agrees with adding all four bars. This is a surviving count, so do not subtract it from the initial 1000 eligible fighters.
G Strategy shortcut
Method: 1980 under 30 becomes 2020 brackets 50–60 and 60–70. Add 140+100+125+105=470.Verification: 1. The starting cohorts below 30 are 10–20 and 20–30 in 1980.
2. Forty years add 40 coins, moving these cohorts to 50–60 and 60–70 in 2020.
3. Read the orange and pale-orange bars, not the other year colours: 50–60 has 140 males and 100 females; 60–70 has 125 males and 105 females.
4. Add both genders across both cohorts: 140+100+125+105=470.
5. Answer: D, 470.
6. Track a cohort diagonally through the chart: add 10 to its bracket for each decade, rather than comparing the same bracket across years.
Trap to avoid: Use the exact requested cohort, statistic or rank condition; the worked check above establishes the result.
G Strategy: Method: 1980 under 30 becomes 2020 brackets 50–60 and 60–70. Add 140+100+125+105=470. Verification: 1. The starting cohorts below 30 are 10–20 and 20–30 in 1980. 2. Forty years add 40 coins, moving these cohorts to 50–60 and 60–70 in 2020. 3. Read the orange and pale-orange bars, not the other year colours: 50–60 has 140 males and 100 females; 60–70 has 125 males and 105 females. 4. Add both genders across both cohorts: 140+100+125+105=470. 5. Answer: D, 470. 6. Track a cohort diagonally through the chart: add 10 to its bracket for each decade, rather than comparing the same bracket across years. Trap to avoid: Use the exact requested cohort, statistic or rank condition; the worked check above establishes the result.