Question 1187218
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7. Find the sum of
a) the positive multiples of 5 up to 500
b) the positive multiples of 7 up to 245
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(a)  S = 5 + 10 + 15 + . . . + 500 = 5*(1 + 2 + 3 + . . . + 100) = {{{5*((100*101)/2)}}} = 5*50*101 = 25250.    <U>ANSWER</U>


     Use the formula of the sum of the first n natural numbers  1 + 2 + 3 + . . . + n = {{{(n*(n+1))/2}}}.
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Part (a) is just solved.



Do part (b) in the same way.