Multiply under associativity –
(i) (4 × 1225) × 25 = 1225 × (4 × 25)
4900 × 25 = 1225 × 100 = 122500
(ii) (4 × 158) × 125 = 158 × (4 × 125)
632 × 125 = 158 × 500 = 79000
(iii) (4 × 85) × 25 = 85 × (4 × 25)
340 × 25 = 85 × 100 = 8500
(iv) (8 × 20) × 125 = 20 × (8 × 125)
160 × 125 = 20 × 1000 = 20000