# Question 19 & 20

Question: Write missed terms in the sequence 1,2,6,12,20,21,…………..,47,56? FPSC AD IB 2017 -2nd batch

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Solution:                             Here in general counting starting 1,2,3,4,5,…….. each number is multiplied by its next number;

1 is multiplied by 2 then comes first term i-e 2

2 is multiplied by 3 then comes second term i-e 6

3 is multiplied by 4 then comes third term i-e 12

4 is multiplied by 5 then comes fourth term i-e 20

5 is multiplied by 6 then comes fifth  term i-e 30

……………………………………………………….

and so on !!!

Question 20: The numbers are -1, 2, and 2/3. Which one is irrational ?

Solution:

Irrational numbers are those numbers in which division process never completes i-e in the answer the digits after point never end

So here we see the division never ends and digits after  ‘.’ never ends i-e 6666666666666666……………….. goes on

so

is a irrational number

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