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There are only four neighbourhoods in a city - Levmisto, Tyhrmisto, Pesmisto and Kitmisto. During the onset of a pandemic, the number of new cases of a disease in each of these neighbourhoods was recorded over a period of five days. On each day, the number of new cases recorded in any of the neighbourhoods was either 0, 1, 2 or 3.

The following facts are also known:

  1. There was at least one new case in every neighbourhood on Day 1.
  2. On each of the five days, there were more new cases in Kitmisto than in Pesmisto.
  3. The number of new cases in the city in a day kept increasing during the five-day period. The number of new cases on Day 3 was exactly one more than that on Day 2.
  4. The maximum number of new cases in a day in Pesmisto was 2, and this happened only once during the five-day period.
  5. Kitmisto is the only place to have 3 new cases on Day 2.
  6. The total numbers of new cases in Levmisto, Tyhrmisto, Pesmisto and Kitmisto over the five-day period were 12, 12, 5 and 14 respectively.

Which of the two statements below is/are necessarily false?

Statement A: There were 2 new cases in Tyhrmisto on Day 3.

Statement B: There were no new cases in Pesmisto on Day 2.

Solution

✅ Correct Option: 2
Slide 1/12

Understanding the set :-

  1. There are four neighbourhoods in a city - Levmisto, Tyhrmisto, Pesmisto and Kitmisto.
  1. During the pandemic, the number of new cases of a disease in each of these neighbourhoods was recorded over a period of five days
  1. On each day, the number of new cases recorded in any of the neighbourhoods was either 0, 1, 2 or 3.

This is a table set, where you are required to find the number of new cases coming in the span of 5 days in each of the four neigbourhoods.

NeighbourhoodsDay 1Day 2Day 3Day 4Day 5Total
Levmisto12
Tyhrmisto12
Pesmisto5
Kitmisto14
Total43

Clue 6 says,

The total numbers of new cases in Levmisto, Tyhrmisto, Pesmisto and Kitmisto over the five-day period were 12, 12, 5 and 14 respectively.

we can directly put this data in the table.

Also the total of all cases will be = 12+12+5+14=4312 + 12+ 5+ 14 = 43

NeighbourhoodsDay 1Day 2Day 3Day 4Day 5Total
Levmisto12
Tyhrmisto12
Pesmisto5
Kitmisto314
Total43

Clue 5 says,

Kitmisto is the only place to have 3 new cases on Day 2.

=> Other then Kitmisto, all neigbourhoods on day 2 will have 0,1,2 cases.

Now we know the total number of cases in Kitmisto = 14

=> only possibility of cases in 5 days for Kitmisto = (3,3,3,3,2)(3, 3, 3, 3, 2) in any order.

NeighbourhoodsDay 1Day 2Day 3Day 4Day 5Total
Levmisto12
Tyhrmisto12
Pesmisto5
Kitmisto314
Total43

Clue 4 says,

The maximum number of new cases in a day in Pesmisto was 2, and this happened only once during the five-day period.

=> Number of cases in Pesmisto will be 0,1

we know,

total number of cases in Pesmisto = 5

=> only possibility = (2,1,1,1,0)(2, 1, 1, 1, 0) in any order.

NeighbourhoodsDay 1Day 2Day 3Day 4Day 5Total
Levmisto12
Tyhrmisto12
Pesmisto5
Kitmisto314
Total43

Statement 3 -

The number of new cases in the city in a day kept increasing during the five-day period.

=> the total number of cases kept increasing everyday.

Now, we know,

Maximum possible new cases in pesmisto = 22

=> The maximum number of cases in the city on day 5 = 3+3+3+2=11 3 + 3 + 3+ 2 = 11

NeighbourhoodsDay 1Day 2Day 3Day 4Day 5Total
Levmisto312
Tyhrmisto312
Pesmisto25
Kitmisto3314
Total1143

Case 1 :

Let us consider the maximum number of cases on Day 5 as 10.

Thus the maximum number of cases possible for the remaining days will be 9, 8, 7, and 6

So, the total number of maximum cases possible for this case will be 40(less than 43)

=> Number of new cases on day 5 = 11

=> All the neighborhoods will have 3 new case except Pesmisto who will have only 2 new cases.

NeighbourhoodsDay 1Day 2Day 3Day 4Day 5Total
Levmisto312
Tyhrmisto312
Pesmisto25
Kitmisto3314
Total101143

Now, , if the number of cases on Day 4 is 9,

the maximum number of cases possible for the remaining days will be 8, 7, and 6.

Thus, the maximum number of cases, in this case, will be 41(less than 43).

So, the number of cases on day 4 will be 10.

NeighbourhoodsDay 1Day 2Day 3Day 4Day 5Total
Levmisto312
Tyhrmisto312
Pesmisto25
Kitmisto3314
Total589101143

Now, if the number of cases on Day 3 is 8,

the number of cases on day 2 will be 7,

and the maximum possible number of cases on Day 1 will be 6.

Thus, the number of cases, in this case, will be 42(less then 43)

Therefore, the total number of cases on day 3 = 9

But clue 3 says,

The number of new cases on Day 3 was exactly one more than that on Day 2.

Therefore, the total number of cases on day 2 = 8

=> total number of cases on day 1 = 43−11−10−9−8=543 - 11- 10- 9- 8 = 5

NeighbourhoodsDay 1Day 2Day 3Day 4Day 5Total
Levmisto1312
Tyhrmisto1312
Pesmisto125
Kitmisto2333314
Total589101143

Clue 1 says,

There was at least one new case in every neighbourhood on Day 1.

=> number of cases on day 1 = (1,1,1,2)(1, 1, 1, 2) in any order

But, we know the possible cases for Kitmisto = (2,3,3,3,3)(2,3, 3, 3, 3)

Therefore, number of cases on day 1 for Kitmisto = 2

and all other neighbourhoods = 1

NeighbourhoodsDay 1Day 2Day 3Day 4Day 5Total
Levmisto13312
Tyhrmisto13312
Pesmisto1125
Kitmisto2333314
Total589101143

Day 4

Total number of days = 10

We know, Pesmisto can have 0,1 cases.

Therefore, to make sum as 10 only possible value = (3,3,1,3)(3, 3, 1, 3)

NeighbourhoodsDay 1Day 2Day 3Day 4Day 5Total
Levmisto1233312
Tyhrmisto1233312
Pesmisto110125
Kitmisto2333314
Total589101143

Day 2,

Kitmisto is the only place to have 3 new cases (clue 5)

=>All other neighbourhoods will have 0,1 or 2 cases

Now, to make sum = 8

Also, Pesmisto can't be more then 1

=> only possibility = (2,2,1,3)(2, 2, 1, 3)

=> Pesmisto on day 3 will have 0 new cases.

and, Levmisto and Tyhrmisto will have 12−3−3−2−1=312 - 3- 3- 2- 1 =3 new cases on day 3.

NeighbourhoodsDay 1Day 2Day 3Day 4Day 5Total
Levmisto1233312
Tyhrmisto1233312
Pesmisto110125
Kitmisto2333314
Total589101143

Statement A: There were 2 new cases in Tyhrmisto on Day 3
False
Statement B: There were no new cases in Pesmisto on Day 2
False
Hence, both Statement a and Statement b are false

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