Find the 20th term of the AP whose 7th term is 24 less than the 11th term, first term being 12.

Explanation

Let the first term, common difference and number of terms of an AP are a, d and n, respectively.
Given that, first term (a)=12.
Now by condition,
` " " 7"th term"(T_(7))=11"th term"(T_(11))-24 " " [:' n"th term of an AP", T_(n)=a+(n-1)d]`
`implies a+(7-1)d=a+(11-1)d-24`
`implies 24=4dimplies d=6`
` :. "20th term of AP", T_(20)=a+(20-1)d`
` " " =12+19xx6=126`
Hence, the required 20th term of an AP is 126.