P takes a days to complete a piece of work. Q takes d days more than P to complete the work. R takes d days more than Q to complete the work. S takes d days less than P to complete the work. T takes d days less than S to complete the work. Which of the following does not hold true? (d > 0)

1) R and S working together take more time to complete the work than Q and T do.
2) Q and S working together take more time to complete the work than R and T do.
3) Q and S working together take less time to complete the work than R and T do
4) R and T working together take less time then P and S do

• 3) Q and S working together take less time to complete the work than R and T do
  
  is not true.
  
  Time taken by Q and S = (a-d)*(a+d)/2a = (a^2-d^2)/2
  Time taken by R and T = (a-2d)*(a+2d)/2a = (a^2-4d^2)/2
  
  so Q and S working together will take 'more' time to complete the work than R and T do.
• 11 years agoHelpfull: Yes(0) No(0)