- If sum of upstream and between downstream speed of a boat is 80 kmph , and the boat travels 90 km . upstream in 3hr Find the time taken by boat to cover 120 km downstream
121/5 hr13/5 hr12/5 hr12/7 hr12/11 hrOption C

let b= speed of the boat

w= speed of water

u= upstream speed= b-w

d= downstream speed = b+w

So u +d= 80

that is b-w+b+w= 80

=>b= 40

40-w= 90/3 = 30

w= 10 kmph

b+w= 120/t

t= 120/50 = 12/5 hr - The difference between simple interest and compound interest of a certain sum of money at 10 % per annum for 2 years is Rs. 40. Then the sum is ;
Rs.5000Rs.4000Rs.6000Rs.7000Rs.8000Option B

CI- SI = P ( r/100 ) ^2

40 = p( 10/100) ^2

=> P= Rs.4000 - Compound interest of a sum of money for 2 years at 4 percent per annum is Rs . 2500 Simple interest of the same sum of money at the same rate of interest for 2 years will be :
Rs.2350Rs.2456Rs.2459Rs.2450Rs.2451Option E

CI= P( 1+r/100 ) ^t – P

2500 = P (( 1-4/100)^2 -1)

=> p= 2500 * 625 / 51=Rs. 30637.25

SI= 30,637.25 * 4* 2/100=Rs.2451 - The are two positive integers a and b . What is the probability that a + b is odd ?
1/21/31/41/51/6Option A

Sum of positive integers is either odd or even.

So the probality = 1/2 - Kailash sells apples at a loss of 44 % but he uses a false scale which is 30 % less than its true weight . Find the loss / gain percent ?
21%22%20%23%24%Option C

Let CP = Rs.100 for 100g

So SP=Rs. 56 for 70g

and SP =Rs. 80 for 100g

loss%=100-80/100 * 100 = 20% - Average age of A ,B and C is 80 years . When D joins them the average age becomes 70 years . A new persons E, whose age is 4 years more than D replaces A and the average of B , C, D and E becomes 75 years . What is the age of A ?
20 yrs21 yrs22 yrs23 yrs24 yrsOption E

A+B+C = 3* 80 = 240 yrs

A+B+C+D= 4* 70 = 280 yrs

D age= 280-240 = 40yrs

=> E age= 40 + 4 = 44 yrs

B+C+D+E age = 75* 4= 300 yrs

B+C age = 300 – 40-44=216

A age = 240-216=24 yrs - The population of sparrows in a particular locality is decreases by certain rate . If the current population of sparrows be 36450 and the ratio of decrease in population for second year and 3rd year be 10 : 9 . What was the population of sparrows 3 years ago ?
50,0005500053,00052,00051,000Option A

Ratio = 10:9

=> 10-9 /10 * 100 = 10%

So p ( 1-10/100 ) ^3 = 36450

p= 50,000 - Tap A can fill a water tank in 25 minutes , tap B can fill the same tank in 40 minutes and tap C can empty the tank in 30 minutes . If all the three taps are opened together , In how many minutes will the tank be completely filled up or emptied ?
31 3/10 minutes26 7/12 minutes34 11/19 minutes24 1/5 minutes31 11/19 minutesOption E

A–> 25

B—>40

C—> -30

Required answer = (25 x 40 x 30) / (40 x 30 + 25 x 30 – 25 x 40)

== 600 / 19 = 31 11/19 minutes - A dog starts to chase a man . When the man goes 20 steps the dog moves 16 steps and 10 steps of the dog are equal to 14 steps of the man . The ratio of the speeds of the dog and the man is :
28 : 2528 : 2528 : 2528 : 2528 : 25Option D

dog : man

Steps –> 16 : 20

distance–> 14 : 10

=224 : 300

speed= 28 : 25 - A train runs with a speed of 400 km/hour. What will be its speed in m/sec?
112.11 m/sec111.11 m/sec113.11 m/sec115.11 m/sec117.11 m/secOption B

Speed in km/ hour =400Speed in m/sec = 400 x 5/18 = 500/9 m/sec = 111.11 m/sec