4×60％+25分只19×40％+25分只19×60％
=4*0.6+19/25*0.4+19/25*0.6
=4*0.6+19/25*(0.4+0.6)
=4*0.6+19/25
=2.4+(19*4)/(25*4)
=2.4+76/100
=2.4+0.76
=3.14