Thread to share memory based kvpy question 2019

please share kvpy 2019 questions
@Samrat_2020 , @Tripathi_2020 @Kushagra_2020 ...


How to remove permanent hardness of water.
Options were heating and sodium hexametaphoshate and 2 other

I got 13,2,36,4

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Sodium hexametaphospate is the answer

except 1st one all are matching .
for 1st one I got 7

Can you tell for the 4th question

What was the interval specified for the 1st one?


I think it was 19

Lemme resolve

It was 13.

As all roots of the form npi/3 are repeating & it asked for solutions.

Got all same.

Same approach but how 13

The thirteen solutions are of the form npi/6, 'n' from 0 to 12.

Can u explain 4th one. How much are you expecting@Abhishek_2020_5

13 solutions is correct

For 4th M=2

Can you give reason for the fourth one.