AP ICET 2017 Shift 1 Paper

Question : 128 of 200

Marks: +1, -0

If the sum to 2n terms of the arithmetic progression 2. 5. 8.....Is equal to the sum to n terms of the arithmetic progression is 57. 59. 61...... then n=

Validate

Solution:

S_N=n/2[2a+(n-1)d]

According to the question,

{2n}/{2}[2×2+(2n-1)3]={n}/{2}[2×57+(n-1)2]

⇒2[4+6n-3]=[114+2n-2]

⇒2+12n=112+2n⇒10n=110

∴n=11

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