ctions":[{"to":"divided-num","from":"survived","color":"green","label":"divide by 80"},{"to":"divided-den","from":"start","color":"green","label":"divide by 80"},{"to":"final","from":"divided-den","color":"orange","label":"simplifies to 1/4"}]},"order":1,"title":"Form and simplify fraction","description":"Put the later number of live bacteria over the starting number. Writing 80/320 earns M1; simplifying to 1/4 earns A1."}]}],"generatedAt":"2026-07-22T12:07:35.687Z","modelVersion":"gpt-5.6-terra+diagrams-1","explanationVersion":"v3"},"options":[]},{"id":"b7a8635b-0e26-4e3d-a01b-e37975e3f05d","label":"c","content":"How many more bacteria were killed at **4%** disinfectant than at **0%** disinfectant in 12 hours? Complete the following steps:\n- Calculate the number of bacteria killed at **4%**\n- Calculate the number of bacteria killed at **0%**\n- Calculate how many more bacteria were killed at **4%** than at **0%**","markscheme":"- Calculates number of bacteria killed at $4\\%$: $325 - 16 = 309$ M1\n- Calculates number of bacteria killed at $0\\%$: $320 - 280 = 40$ M1\n- Subtracts to find difference: $309 - 40 = 269$ A1","marks":3,"order":2,"markingRubric":null,"explanation":{"methods":[{"id":"compare_killed","label":"Compare bacteria killed","steps":[{"type":"text","order":1,"title":"Choose the four counts","content":"Read the two rows needed from Table 1: at 4%, the live-bacteria count changes from 325 at 0 hours to 16 at 12 hours. At 0%, it changes from 320 to 280.\n\nFor each concentration, bacteria killed = starting number − number after 12 hours.","highlights":[{"text":"How many more bacteria were killed at **4%** disinfectant than at **0%** disinfectant in 12 hours?","location":"specification"}]},{"type":"hyper_latex","block":{"nodes":[{"latex":"325-16=\\htmlData{anchor=killed4}{309}"},{"text":"This is the number killed."}],"highlights":[{"color":"green","style":"box","anchor":"killed4"}]},"order":2,"title":"Find the 4% decrease","description":"Subtract the final count from the starting count. This calculation earns M1."},{"type":"hyper_latex","block":{"nodes":[{"latex":"320-280=\\htmlData{anchor=killed0}{40}"},{"text":"This is the number killed."}],"highlights":[{"color":"green","style":"box","anchor":"killed0"}]},"order":3,"title":"Find the 0% decrease","description":"Use the same subtraction for the tube with no disinfectant. This earns the second M1."},{"type":"hyper_latex","block":{"nodes":[{"latex":"309-40=\\htmlData{anchor=difference}{269}"},{"text":"Therefore, 269 more bacteria were killed at 4% disinfectant."}],"highlights":[{"color":"green","style":"box","anchor":"difference"}]},"order":4,"title":"Compare numbers killed","description":"Subtract the number killed at 0% from the number killed at 4%. This correct comparison earns A1."}]}],"generatedAt":"2026-07-22T12:15:46.785Z","modelVersion":"gpt-5.6-terra+diagrams-1","explanationVersion":"v3"},"options":[]},{"id":"c007d026-b259-41a6-94c5-1a86700390e9","label":"d","content":"A student calculated value **Y** in Table 1 to be 180.\nSuggest how the student calculated this value.","markscheme":"- States that the student took the average / mean / midpoint of the 12-hour values for $0\\%$ and $2\\%$ concentrations M1\n- Shows calculation: $\\frac{280 + 80}{2} = 180$ A1","marks":2,"order":3,"markingRubric":null,"explanation":{"methods":[{"id":"midpoint_estimate","label":"Estimate using the midpoint","steps":[{"type":"text","order":0,"title":"Choose neighbouring values","content":"The missing value $Y$ is at a disinfectant concentration of $1\\%$. At $12$ hours, this lies midway between the given concentrations of $0\\%$ and $2\\%$, whose numbers of live bacteria are $280$ and $80$. So the student used the **mean (average)** of these two values. Identifying this method earns **M1**.","highlights":[{"text":"Suggest how the student calculated this value.","location":"specification"}]},{"type":"hyper_latex","block":{"nodes":[{"latex":"$$Y=\\dfrac{\\color{@sky}{\\htmlData{anchor=values}{280

Year	Number of cholera cases per 100,000 people
2010	200
2012	168
2014	140
2016	118
2018	110
2020	105

Year	Number of cholera cases per 100,000 people
2010	200
2012	168
2014	140
2016	118
2018	110
2020	105

3.1 Communicable diseases

Question 3

3.1 Communicable diseases Questions

3.1 Communicable diseases

Question 3

3.1 Communicable diseases Questions