what is the sum of the number 78 to 220?
220 - 78 =142 + 1 =143 Number of terms.
Sum =[F + L] / 2 x N, where F=First term, L=Last term, N=Number of terms.
Sum =[78 + 220] / 2 x 143 =
Sum =[298]/2 x 143 =
Sum = 149 x 143 = 21,307.
Just use the calculator.
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