We have a big playground in our school .We all like to 1 games 2 after school .It's Friday .We have only two classes 3 the afternoon . 4 school is over（结束的）,a lot of students go to the playground quickly.  The boys of Grade Two often 5 soccer. The girls like 6 them playing .Soccer is their favorite sport . Their teacher Mr Li also 7 football. Li Ming , Li Lei and Wei Fang are students of Grade One .They sometimes play 8 the students of Class Two. It’s half past five 9 . It's time 10dinner . My father is waiting for me at the school gate .

读“天体系统示意图”，完成下题．

谚语是我国劳动人民语言智慧的结晶，很多谚语与生物学现象有关．下列谚语中能够说明“生物影响环境”的是（  ）

两个自然数的和与差的积是41，那么这两个自然数的和是____。

所用时间为t₂,下山时平均速度保持为4v,已知小明上山的路程和下山的路程是相同的,那么

小明下山用时____.