Question

51+50+49+ ..... + 21= .....

• A. 1116
• B. 1122
• C. 1128
• D. 1124

Answer 1

Answer:

A. 1116

a=51,d=-1 അവസാന പദം=21 n=((21-51)/-1)+1 =31 Sn=31/2*(2a+30d) =31/2(102-30) =1116