Question

the average of first seven multiple of3 is

Answer 1

3, 6, 9, ...........21
Sn= n÷2 { 2a + (n-1)d}
7÷2 { 2×3 + (7-1) 3}
7÷2 { 6+18}
7÷2{24}
7×12
=84
average= total sumof terms÷no. of terms
= 84÷7
= 12
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