3/5*1/4*2+7/10*1/4*2+3/5*7/10*2=107/100
3/5*1/4*2+3/5*7/10*2+1/4*7/10*2就是（长*宽）*2+（长*高）*2+（宽*高）*2
S=(ab+ac+bc)x2 =(3/5x1/4+3/5x7/10+1/4x7/10) =59/2000(m)
2×（3/5*1/4+3/5*7/10+1/4*7/10)
3/5乘1/4乘7/10=0.105(平方米)
