a) 37 x 99999 = 37 x 100000 - 37 = 3700000 - 37 = 3699963
b) 45 x 10001 = 45 x 10000 + 45 = 450000 + 45 = 450045 .
c) 125125 x 72 = 125125 x 70 + 125125 x 2 = 87588750 + 250250 = 87839000
d) 252525 x 36 = 252525 x 30 + 252525 x 6 = 7575750 + 1515150 =9090900