ANSWER : 1 hour and 15 minutes

Explanation : : Rate of waste pipe more,the tank will be emptied when all the three pipes are opened. Net emptying workdone by both in 1 hour =(1/3+4/15)-1/1 =(5+4 /15)-1/1=9/15-1=-6/15 (-ve sign means emptying) Now,full tank will be empited by 15/6 hours (or) 2 hours and 30 minutes Half full tank will be empited by 1 hour and 15 minutes

ANSWER : 36 hours

Explanation : : Cistern will be filled in 1 hour =(1/12-1/8) =18-12 / 12 x18=6/12 x 18=1/36 The tank will be filled in 36 hours

ANSWER : 15%

Explanation : : First discount=10% Second discount =y% 90% of (100-Y)% of 1600=Rs.1224 90/100 x 100-y/100 x 1600=1224 100-y=1224 x 100 x 100 /1600 x 10 =85 y=100-85=15% Second discount=15%

ANSWER : 6 2/3%

Explanation : : Marked price=Rs.100 10% discount=10/100 x 100=Rs.10 After discount,the marked price=Rs.100-10=Rs.90 Cost price=120/100x=90 x=90 x 100/120 =Rs.75 then,20% discount=20/100 x 100=Rs.20 After discount,the marked price=100-20=Rs.80 Gain=80-75=Rs.5 Gain % =5/75 x 100=6 2/3%

ANSWER : Rs 1,795.50

Explanation : : List price of an article =Rs.2100 10% discount=10/100x2100=210 After discount,the list price=2100-210=1890 During off-season, 5% discount=5/100 x 1890=94.50 After discount,the selling price=1890-94.50=Rs.1795.50