Solving under associativity
(i) 72 + 44 + 94= (70 + 2) + (40 + 4) + (90 + 4)
= (70 + 40 + 90) + (2 + 4 + 4) = 200 + 10 = 210
(ii) 51 × 63 × 47 = 51 × (60 + 3) × 47
= (51 × 60 + 51 × 3) × 47 = (3060 + 153) × 47
= 3213 × 47 = 3213 × (40 + 7)
= 3213 × 40 + 3213 × 7 = 128520 + 22491 = 151011