Weighted Average

#1
Hello - is it possible to find the weighted average of the below numbers? I've tried looking online, but all I can find is the formula to multiply by the weighted average - how do I find that?

Code:
    Size    Sales
Product 1    73,900    $86,054
Product 2    75,255    $48,747
Product 3    54,098    $61,908
Product 4    55,396    $61,554
Product 5    55,750    $42,589
Product 6    81,780    $61,701
Product 7    55,014    $36,360
Product 8    66,626    $54,133
Product 9    80,725    $72,511
Product 10    62,150    $47,900
Product 11    73,000    $59,902
Product 12    38,582    $24,140
Product 13    69,496    $59,489
Product 14    69,385    $59,712
Product 15    59,875    $35,257
Product 16    63,525    $62,295
Product 17    60,250    $57,946
Product 18    61,700    $58,106
Product 19    69,352    $54,555
Product 20    46,760    $50,248
Product 21    61,398    $42,732
Product 22    60,580    $51,621
Product 23    84,730    $50,139
Product 24    32,162    $67,058
Product 25    83,141    $49,807
Product 26    68,595    $49,948
Product 27    73,350    $105,236
Product 28    78,945    $81,574
Product 29    40,150    $30,071
Product 30    75,500    $54,788
Product 31    56,496    $30,112
Product 32    60,395    $77,248
Product 33    88,810    $86,778
Product 34    62,660    $39,894
Product 35    66,004    $74,180
Product 36    86,458    $42,158
Product 37    42,675    $31,214
Product 38    92,395    $69,358
Product 39    66,270    $117,159
Product 40    112,060    $94,524
Product 41    76,547    $63,545