Q.

A building construction work can be completed by two masons A and B together in 22.5 days. Mason A alone can complete the construction work in 24 days less than mason B alone. Then mason A alone will complete the construction work in:                  [2026]

1 24 days  
2 36 days  
3 42 days  
4 30 days  

Ans.

(2)

Let time taken by mason A alone to complete the work be x days.

So, mason B alone takes (x+24) days.

Work done by A in 1 day=1x

Work done by B in 1 day=1x+24

Work done by A + B in 1 day=122.5

So, 1x+1x+24=122.5=245

1x+1x+24=245

2x+24x(x+24)=245

45(2x+24)=2x(x+24)

90x+1080=2x2+48x

2x2-42x-1080=0

x2-21x-540=0

x=36  or  x=-15

x=-15 (rejected)

Ans.=36 option (2)