Divide 30, 42, 55, 66, 78 and 91 into two groups to make the product of each group equal
30 = 2 × 3 × 542 = 2 × 3 × 755 = 5 × 1166 = 2 × 3 × 1178 = 2 × 3 × 1391 = 7 × 1330 × 42 × 55 × 66 × 78 × 91 = 2 × 2 × 2 × 2 × 3 × 3 × 3 × 5 × 7 × 7 × 11 × 13 × 132 × 2 × 3 × 5 × 7 × 11 × 13 = 180180 = 30 × 66 × 91 = 42 × 55 × 78