How many term of the A.P 8,15,22........... add upto 1490?

Dear Student,

8, 15, 22,...........nSn=1490a=8, d=15-8=7Sn= n2[2a+(n-1)d]1490=n2[16+(n-1)7]1490=n2[16+7n-7]2980=n[9+7n]2980=9n+7n27n2+9n-2980=0n=-9±92-4(7)(-2980)2×7n=-9±8352114n=-9+28914 (As n cannot be negative)n=20

Regards

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