b) 25 x 20 x 125 x 8 - 8 x 20 x 5 x 125
= 25 x 20 x 25 x 5 x 8 - 8 x 20 x 5 x 5 x 25
= 25 x 20 x 25 x 40 - 8 x 10 x 25 x 25
= 500 x 1000 - 80 x 625
= 500 000 - 50000
= 450000
25 x 20 x 125 x 8 - 8 x 20 x 5 x 125
= 25 x 20 x 25 x 5 x 8 - 8 x 20 x 5 x 5 x 25
= 25 x 20 x 25 x 40 - 8 x 20 x 25 x 25
= 500 x 1000 - 160 x 625
= 500 000 - 100000
= 400000
25 x 20 x 125 x 8 - 8 x 20 x 5 x 25
= (125 x 8) x 20 x (25 - 5)
= 1000 x 20 x 20
= 1000 x 40
= 40000
25×20×125×8-8×20×5×125
=500000-100000
=400000