This seems a bit extreme, but it does show the point of social distancing.
Once it goes below one person infecting one person per 5 days, it drops off drastically.
I found this chart in a newspaper, but when I work out the changes I get different results.
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1 person (No Lockdown) x 5 days
2.5 x 5 = 12.5
12.5 x 5 = 62.5
62.5 x 5 = 327.5
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1 person (Lockdown) x 5 days
1.25 x 5 = 6.25
6.25 x 5 = 31.25
31.25 x 5 = 157.5
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After peak x 5 days
(Assuming people that are positive and can spread the virus for 10 days) It should accelerate once below 1:1 person passing on the virus
300 people infected.
300 x 0.50 = 150 (5 days)
150 x 0.50 = 75 (5 days)
75 x 0.50 = 37 (5 days)