Find the mean of the first 25 multiples of 10
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Answer:
The average = 5(1+25)/2 = 5*13 = 65.
Method 2. Sum of 25 terms of an Ap whose first term is 5 and common difference = 5 is
S25 = (25/2)[2*5 + (25–1)*5]
= (25/2)[10+24*5]
= (25/2)[10+120]
= 25*130/2
= 1625
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