3274a-86a5-421a-a825-3369138f8900","label":"b","content":"What fraction of the bacteria present at 0 hours for **4%** tea tree oil concentration survived for 16 hours? Give your answer in its simplest form.","markscheme":"- Identifies 480 at 0 hours and 96 at 16 hours for the 4% concentration M1\n- Calculates the fraction as $\\frac{96}{480} = \\frac{1}{5}$ A1","marks":2,"order":1,"markingRubric":null,"explanation":{"methods":[{"id":"survival_fraction","label":"Find the survival fraction","steps":[{"type":"text","order":1,"title":"Read the two values","content":"Stay in the **4%** column. At $0$ hours there are $480$ live bacteria, and at $16$ hours there are $96$.\n\nFor a fraction that survived, use\n\n$$\\frac{\\text{number alive at 16 hours}}{\\text{number present at 0 hours}}$$\n\nIdentifying these two table values earns **M1**.","highlights":[{"text":"**4%**","location":"specification"},{"text":"0 hours","location":"specification"},{"text":"16 hours","location":"specification"}]},{"type":"hyper_latex","block":{"nodes":[{"latex":"\\text{fraction survived}=\\frac{96}{480}"},{"latex":"\\frac{96}{480}=\\htmlData{anchor=answer}{\\frac{1}{5}}"}],"highlights":[{"color":"green","style":"box","anchor":"answer"}]},"order":2,"title":"Form and simplify","description":"Put the later number over the starting number. Using 96/480 and simplifying to 1/5 earns A1."}]}],"generatedAt":"2026-07-22T12:07:49.633Z","modelVersion":"gpt-5.6-terra+diagrams-1","explanationVersion":"v3"},"options":[]},{"id":"ac7eb414-4463-4329-860a-e4eb8f23732f","label":"c","content":"How many more bacteria were killed at **8%** concentration than at **0%** concentration in 16 hours? Complete the following steps:\n- Calculate the number of bacteria killed at **8%**\n- Calculate the number of bacteria killed at **0%**\n- Calculate how many more bacteria were killed at **8%** than at **0%**","markscheme":"- Calculates bacteria killed at 8%: $485 - 15 = 470$ B1\n- Calculates bacteria killed at 0%: $480 - 400 = 80$ B1\n- Finds the difference: $470 - 80 = 390$ A1","marks":3,"order":2,"markingRubric":null,"explanation":{"methods":[{"id":"compare_bacteria_killed","label":"Compare the bacteria killed","steps":[{"type":"text","order":0,"title":"Compare the two times","content":"For each concentration, subtract the number of **live bacteria after 16 hours** from the number at **0 hours**. This gives the number killed during the investigation. Use the two rows in Table 1, rather than comparing the two concentrations directly.","highlights":[{"text":"How many more bacteria were killed at **8%** concentration than at **0%** concentration in 16 hours?","location":"specification"}]},{"type":"hyper_latex","block":{"nodes":[{"latex":"\\text{bacteria killed at }8\\% = 485 - 15"},{"latex":"\\text{bacteria killed at }8\\% = \\htmlData{anchor=answer_8}{470}"}],"highlights":[{"color":"teal","style":"box","anchor":"answer_8"}]},"order":1,"title":"Calculate the 8% deaths","description":"At 8%, there were 485 live bacteria at the start and 15 left after 16 hours. Subtract to find how many were killed; this earns the first B1 mark."},{"type":"hyper_latex","block":{"nodes":[{"latex":"\\text{bacteria killed at }0\\% = 480 - 400"},{"latex":"\\text{bacteria killed at }0\\% = \\htmlData{anchor=answer_0}{80}"}],"highlights":[{"color":"orange","style":"box","anchor":"answer_0"}]},"order":2,"title":"Calculate the 0% deaths","description":"At 0%, use the same subtraction: start number minus the live number after 16 hours. This earns the second B1 mark."},{"type":"hyper_latex","block":{"nodes":[{"latex":"\\text{more killed at }8\\% = 470 - 80"},{"latex":"\\text{more killed at }8\\% = \\htmlData{anchor=final_answer}{390}"}],"highlights":[{"color":"green","style":"box","anchor":"final_answer"}]},"order":3,"title":"Find how many more","description":"Now compare the two numbers killed. Subtract the 0% result from the 8% result; this is the final A1 mark."}]}],"generatedAt":"2026-07-22T12:10:18.245Z","modelVersion":"gpt-5.6-t

Year	Number of Tuberculosis (TB) cases per 100,000 people
2011	350
2013	295
2015	247
2017	210
2019	195
2021	187

Year	Number of Tuberculosis (TB) cases per 100,000 people
2011	350
2013	295
2015	247
2017	210
2019	195
2021	187

3.1 Communicable diseases

Question 6

3.1 Communicable diseases Questions

3.1 Communicable diseases

Question 6

3.1 Communicable diseases Questions