If a boy rows 8 km downstream in 6 hours and 4 km upstream in 4 hours then how long will he take to cover 16 km in stationary (still) water?

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• A number is reduced by 10%. Its present value is 1080. What was its original value?

  (A) 2300
  (B) 3250
  (C) 1980
  (D) 1200

  ►Correct Option
  
  Correct Option is: D
  Original value is percentage = 100 %.
  Reduce amount in percentage = 10 %
  Therefore, Percent value in percentage = 100 % – 10 % = 90 %.
  According to the problem,
  90 % of original value = 1080
  Therefore, 100 % of original value = 1080/100 × 90 = 1200.
  Thus, the original value was 1200.
  
  

• Find the number which when decreased by 24 % becomes 594?

  (A) 781.5
  (B) 398.5
  (C) 625.8
  (D) 465.7

  ►Correct Option
  
  Correct Option is: A
  Let the number be m.
  Decrease = 24 % of m
  = 24/100 × m = 6m /25
  Therefore, decrease number = m – 6m/25 = (25m – 6m)/25 = 19m/25
  According to the question 19m/25 = 594
  19m = 594 × 25
  19m = 14850
  m = 14850/19
  m =781.5
  

• A number 168 was misread as 24. Find the reading error in percent.

  (A) 85.7%
  (B) 42.6%
  (C) 98.6%
  (D) 67.4%

  ►Correct Option
  
  Correct Option is: A
  Error = 168 – 24 = 144
  Therefore, % error = 144/168
  [Since, we know decrease% = decrease in value/original value × 100 %]
  = 144/168 × 100
  = 85.7 %
  

• A wooden manufacturing company declares that a wooden is now available for $11200 as against $25200 one year before. Find the percentage reduction in the price of wooden offered by the company?

  (A) 25 1/3%
  (B) 55 5/9%
  (C) 66 1/3%
  (D) 69 1/3%

  ►Correct Option
  
  Correct Option is: B
  Price of the wooden a year before = $25200
  Price of the wooden after a year = $11200
  Decrease in price = $(25200 – 11200) = $14000
  Therefore, decrease % = 14000/25200 × 100 %
  = 55 5/9 %
  

• The cost of a stencil is decreased by 30%. If the original cost is $140 find the decrease cost?

  (A) $25
  (B) $45
  (C) $68
  (D) $98

  ►Correct Option
  
  Correct Option is: D
  Original cost = $140
  Decrease in it = 30% of $140
  = 30/100 × 140
  = 4200/100
  = $42
  Therefore, decrease cost = $140 – $42 = $98
  

• A taxi driver make a trip from the plains to ooty which are 340 km apart at an average speed of 60 km/hr. In the return trip, he covers the speed distance at an average of 30 km/hr. The average speed of the taxi over the entire distance of 680 km is:

  (A) 30 km/hr
  (B) 40 km/hr
  (C) 50 km/hr
  (D) 60 km/hr

  ►Correct Option
  
  Correct Option is: B
  Average speed =(2xy/( x+y)) km/hr
  Given x =60 km/hr y = 30km/hr
  Average speed = (2*60*30/ (60+30)) km/hr
  =(3600/ 90)
  =40 km/hr
  

• Anitha takes 8 hours 20 mints in walking to a temple and riding back. She would have gained 3 hours by riding both ways. The time she would take to walk both ways is:

  (A) 15 hours 40 mints
  (B) 16 hours 40 mints
  (C) 18 hours 40 mints
  (D) 19 hours 40 mints

  ►Correct Option
  
  Correct Option is: D
  Let the distance be x km. then,
  (time taken to walk x km)+(time taken to ride x km) = 25/3 hrs
  (time taken to walk 3x km)+(time taken to ride 3x km) = 25/3*3 =25hrs
  But the time taken to ride 3xkm=(25/3 – 3)hrs
  =(25 – 9)/3 hrs
  =16/3 hrs
  Time taken to walk 3x km = (25 – 16/3)hrs
  =(75 – 16)/3
  =59/3
  =19 hours 40 mins
  

• Jackson travels a distance of 100 km in 5 hours. How much faster in kilometer per hour, on an average, must he travel to make a journey in 5/3 hour less time?

  (A) 5 km/hr
  (B) 6 km/hr
  (C) 8 km/hr
  (D) 10 km/hr

  ►Correct Option
  
  Correct Option is: D
  Time required = (5 hrs – 5/3 hrs)
  =(5 hrs – 100 mints)
  = (5 hrs – 1hr 40 mints)
  = 3 hrs 20 mints
  = 3 1/3 hrs
  Required speed = (100*3/10) km/hr
  =30 km/hr
  Original speed = (100/5)km/hr = 20 km/hr
  Difference speed = required speed – original speed
  =(30-20)
  =10km/hr