In which year the school had the best result for H.S. in respect of percentage of pass candidates ?

No. of pass students in 2008 = 20+60+60 = 140

Total students in 2008 = 170

=> % of pass students in 2008 = $$\frac{140}{170}$$ * 100 = 82.35%

No. of pass students in 2009 = 30+60+50 = 140

Total students in 2009 = 190

=> % of pass students in 2009 = $$\frac{140}{190}$$ * 100 = 73.68%

No. of pass students in 2010 = 40+60+70 = 170

Total students in 2010 = 200

=> % of pass students in 2010 = $$\frac{170}{200}$$ * 100 = 85% [MAX]

Thus, in 2010 the school has the best result.