172.4×6.2+2724×0.38
=172.4×6.2+（1724+1000）×0.38，
=172.4×6.2+1724×0.38+1000×0.38，
=172.4×6.2+172.4×3.8+380，
=172.4×（6.2+3.8）+380，
=172.4×10+380，
=1724+380，
=2104．