QUESTION
If a man cycles at 10 km/hr, then he arrives at a certain place at 1 p.m. If he cycles at 15 km/hr, he will arrive at the same place at 11a.m. At what speed must he cycle to get there at noon?
1) 11 km/hr
2) 12 km/hr
3) 13 km/hr
4) 14 km/hr*
ANSWER
ANS : 2*10*15/25 = 60/5 = 12
since the times are 1pm,12 pm , 11 pm are in AP , speeds should be in HP. for 12 PM ==> HM(10,15) = 2*10*15 /(10+15) = 12.