7. If 4 examiners can examine a certain number of answer books in 8 days by working 5 hours a day; for how many hours a day would 2 examiners have to work in order to examine twice the number of answer books in 20 days ?

8. If 22.5 metres of a uniform iron rod weighs 85.5 kg., what will be the weight of 6 meters of the same rod ?

9. A contractor undertook to do a certain piece of work in 9 days. He employed certain number of labouters but 6 of them being adsent from the very first day, the rest could finish the work in 15 days. The number of men originally employed were :