Sum of last two terms of an A.P. is 60. If first termis 11 and common

1.	Sum of last two terms of an A.P. is 60. If first termis 11 and common differences 2, then the numberof terms in the A.P. is(a) 2(c) 11(b) 20(d) 19
Answer» a=11d=2Let number of terms be n+1an+an-1=60a+(n-1)d + a+(n+1-1)d=6011+(n-1)2 + 11+n(2)=6022+2n-2+2n=604n+20=604n=60-20=40n=40/4=10 Number of terms are 11Option c is correct

Sum of last two terms of an A.P. is 60. If first termis 11 and common differences 2, then the numberof terms in the A.P. is(a) 2(c) 11(b) 20(d) 19

Answer»

a=11d=2Let number of terms be n+1an+an-1=60a+(n-1)d + a+(n+1-1)d=6011+(n-1)2 + 11+n(2)=6022+2n-2+2n=604n+20=604n=60-20=40n=40/4=10

Number of terms are 11Option c is correct