为什么half前不加a而quarter前加a

为什么half前不加a而quarter前加a half past 0ne ,前不加a,而 a quarter tohalf past 0ne ,前不加a,而 a quarter to f0ur,前为什么加a? 为什么可以说a quarter past 而不能说a half past 关于英语：为什么half past one不加a；而 a quarter past one要加aI need to explain. a quarter and a half It's a quarter past ten和It‘s half past ten为什么quarter前面加a ,half不加? A half and a quarter is ______. they arrived a quarter to eleven.a quarter to eleven前为什么没有加at a quarter past half 的意思 two and a half 和 three and a quarter为什么two and a half是 212 而three and a quarter 是314的意思?帮忙解释一下,谢谢了!这二个短语在这里表示的是数字,二百一十二和三百一十四! a quarter to eight half past six a quartera quarter to eight half past six a quarter past seven a quarter to five eight o,clock是几点 have sport at a quarter Past four.It's quarter past eight 为什么前一个用a,后一个不用 three quarter of a book为什么quarter没用复数 基础英语.Half a pound of coffee.A quarter of a pound of tea.为什么第二句前面有A,第一句却没 half前 什么时候加a Ten past seven是7点过10分吗past（表示半点前）Ten past seven.half past eight.Ten to seven.Twenty to four.A quarter past one.a quarter to four.a quarter past nine.各是表示几点?// have sport at a quarter past four.it's quarter past eight .为什么前一个用a quart 后...have sport at a quarter past four.it's quarter past eight .为什么前一个用a quart 后一个不用a而后一个不用a 根据英文写出相应的时间1） half past six 2) ten past twelve 3) half past twelve 4) a quarter past nine5) a quarter to two