设甲乙要做X个,则甲乙的效率比是:X/4:(X-45)
[X(1-1/4)*2/3]/(X/4*120%)=(45-X/3)/(X-45)
(1/2)/(3/10)=(45-X/3)/(X-45)
45-X/3=5/3(X-45)
45-X/3=5/3X-75
2X=120
X=60
即甲乙要做60个
设甲乙要做X个,则甲乙的效率比是:X/4:(X-45)
[X(1-1/4)*2/3]/(X/4*120%)=(45-X/3)/(X-45)
(1/2)/(3/10)=(45-X/3)/(X-45)
45-X/3=5/3(X-45)
45-X/3=5/3X-75
2X=120
X=60
即甲乙要做60个