NCERT Maths solution class 10 chapter 5 arithmetic progressions exercise 5.2 question number 12,this is a very common question student face problem in solving. Here Two A.P’s have same common difference (d) and difference of their 100th term is given to us as 100, you need to find the difference between their 1000th term.

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let, the first term of AP 1 be

a_{1}and the first term of AP 2 isa_{2,}because common difference is given same for both the AP’s

∴ let the common difference of both AP’s be

d.to find the nth tern we have a formula,

a=_{n}a+(n−1)dTherefore, For the first A.P.,we know,a_{100}=a_{1}+(100−1)d=

a_{1}+ 99d&

a_{1000}=a_{1}+(1000−1)da_{1000}=a_{1}+999dsimilarly,For second A.P.,

a_{100}=a_{2}+(100−1)d=

a_{2}+99d&

a_{1000}=a_{2}+(1000−1)d=

a_{2}+999dIt is Given that, difference between 100

^{th}term of the two APs = 100Therefore, (

a_{1}+99d) − (a_{2}-99d) = 100Therefore,a_{1}+99d−a_{2}-99d= 100∴

a_{1}−a_{2}= 100………………………………………………………………..(i)Difference between 1000

^{th}terms of the two AP’s is(

a_{1}+999d) − (a_{2}+999d) =a_{1}−a_{2}From equation

(i),This difference,

a_{1}−a_{2 }= 100Hence, the difference between 1000

^{th}terms of the two A.P. will be 100.