(1)45.5+16.9+5.5
=45.5+5.5+16.9
=51+16.9
=67.9;
(2)25×98+25×3-25
=25×(98+3-1)
=25×100
=2500;
(3)10.01-3.69+4.99-2.31
=(10.01+4.99)-(3.69+2.31)
=15-6
=9;
(4)125×31×8×3
=(125×8)×(31×3)
=1000×93
=93000;
(5)4000÷25
=(4000×4)÷(25×4)
=16000÷100
=160;
(6)15×[(400-16)÷24]
=15×[384÷24]
=15×16
=240.