20% of a number when added to 20 becomes the  number itself,then the number is

Which one of the following is correct? 

The sum of first 47 terms of the series (1/4+1/5-1/6-1/4-1/5+1/6+1/4+1/5-1/6... is

Three athletes run a 4km race.Their speeds are in the ratio 16:15:11.When the winner wins the race,distance between the athlete in the second position to the athlete in the third position is

If a:b=3:5 and b:c=7:8 ,then 2a:3b:7c is equal to

If m persons can paint a house in d days,how many days will it take for (m+2) persons to paint the same house?