Question 73

What is the average of all the multiples of 6 from 20 to 80?

Solution

Sum of no. = $$\frac{no.\ of\ term}{2}\times(first\ term+last\ term)$$

Avg = $$\frac{sum\ of\ no.}{no.\ of\ term}$$

= $$\frac{first\ term+Last\ term}{2}$$

First term which is multiplied by 6 after 20 is 24 and last no. Is 78

=$$\frac{24 +78}{2}$$

=51

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