Practical_placement

A man rows ‘k’ km upstream and back again downstream to the same point in H hours. The speed of rowing in still water is s km/hr and the rate of stream is r km/hr. Then

• (s^2-r^2) =2sk /H

•  (r + s) = kH / (r -s)

• rs = kH

•  None of the above

Answer explanation

Option A

Time taken to cover total distance = H hrs.
Speed of upstream = s - r. Speed of downstream = s + r.
∴ k / (s + r) + k / (s - r) = H ⇒(s2-r2) =2sk /H

The captain of a cricket team of 11 members is 26 years old and the wicket keeper is 3

years older. If the ages of these two are excluded, the average age of the remaining

players is one year less than the average age of the whole team. What is the average

age of the team?

• 23 years

• 24 years

• 25 years

• None of these

Answer explanation

Option A

Explanation:

Let the average age of the whole team by x years.

11x - (26 + 29) = 9(x -1)

11x - 9x = 46

2x = 46

x = 23.

So, average age of the team is 23 years.

A water tank has two pipes to fill water in it. One of the pipes fills water at the rate of 100 litres per hour. The tank is filled by the other pipe in 6 hours and by both pipes together in 4.2 hours. What is the capacity of the tank in litres ?

• 860 litre

• 980 litre

• 1120 litre

• 1400 litre

Suppose a fair six-sided die is rolled once. If the value on the die is 1, 2, or 3, the die is rolled a second time. What is the probability that the sum total of values that turn up is at least 6?

• 10/21

• 5/12

•  2/3

• 1/6

Two trains running in opposite directions cross a man standing on the platform in 27 seconds and 17 seconds respectively and they cross each other in 23 seconds. The ratio of their speeds is:

• 1:3

• 3:2

• 3:4

• None of these

Answer explanation

Let the speeds of the two trains be x m/sec and m/sec respectively.

Then, length of the first train = 27x metres, and length of the second train = 17y metres. (27x + 17y)/(x + y) = 23

27x + 17y = 23x + 23j

4x = 6v

x/y = 3/2

A farmer travelled a distance of 61 km in 9 hours. He travelled partly on foot @ 4 km/hr and partly on bicycle @ 9 km/hr. The distance travelled on foot is:

• 14 km

• 15 km

• 16 km

• 17 km

Answer explanation

Let the distance travelled on foot be x km.

Then, distance travelled on bicycle = (61 -x) km.

So,

x

+

(61 -x)

= 9

4

9

 9x + 4(61 -x) = 9 x 36

 5x = 80

x = 16 km.

Q is as much younger than R as he is older than T. If the sum of the ages of R and T is

50 years, what is definitely the difference between R and Q's age?

• 1 year

• 2 years

• 25 years

• Data inadequate

Answer explanation

1. The difference of age b/w R and Q = The difference of age b/w Q and T.

2. Sum of age of R and T is 50 i.e. (R + T) = 50.

Question: R - Q = ?.

Explanation:

R - Q = Q - T

(R + T) = 2Q

Now given that, (R + T) = 50

So, 50 = 2Q and therefore Q = 25.

Question is (R - Q) = ?

Here we know the value(age) of Q (25), but we don't know the age of R.

Therefore, (R-Q) cannot be determined.

The cost price of 20 articles is the same as the selling price of x articles. If the profit is 25%, then the value of x is:

• 15

• 25

• 18

• 16

Find out the wrong number in the series.

445, 221, 109, 46, 25, 11, 4

• 221

• 109

• 46

• 25

What is the speed of the train whose length Is 210 metres?

1. The train crosses another train (Howrah Express/12869) of 300 metres length running in opposite direction in 10 seconds.

II. The train crosses another train (Howrah Express/12869) running in the same direction at the speed of 60 km/hr in 30 seconds

• I alone sufficient while II alone not sufficient to answer

• II alone sufficient while I alone not sufficient to answer

• Either l or II alone sufficient to answer

• Both I and II are not sufficient to answer

• Both I and II are necessary to answer