Missing Number 1 - Answer

View the Question Missing Number

 

 

58

The number in the center is the sum of the products of  the numbers above and below it.

So,

6 * 7 + 3 * 9 = 42 + 27 = 69

3 * 6 + 8 * 4 = 18 + 32 = 50

5 * 8 + 2 * 9 = 40 + 18 = 58

Age Problems - Answer

View the Question Age Problems

 

Answer (1)

39 years

Let the person's age be x, and that of his son be y.

Then, x = 3y
And,  x + 13 = 2 (y + 13)

Solving them, we get  3y + 13 = 2y + 26
or y = 13
So the persons age = 3y = 39

Answer (2)

34 years

Let the man's current age by x, and that of his son be y.

Two years ago,
x - 2 = 4 (y - 2)
x - 2 = 4y - 8
x = 4y - 6

Two years from now,
x + 2 = 3 (y + 2)
x + 2 = 3y + 6
x = 3y + 4

So, 4y - 6 = 3y + 4
i.e. y = 10
x = 4y -6 = 40 - 6 = 34

Answer (3)

Their ages are 15 years, 17 years and 45 years.

Let the ages of youngest son, older son and the father be x, y and z respectively.

Then,
x + y =32
y + 28  = 3x = z

which gives,
x - 28 = 32 - 3x
4x = 60
x = 15 years
y = 17 years
 z = 45 years

Number Series 2 - Answer

View the Question on Number Series

 

13, 16, 49, 169, ___

16 = (1+3)²,
49 = (1+6)²,
169 = (4+9)²,

So the next term = (1+6+9)² = 16² = 256

Speed and Time 1 - Answer

View the Question Speed and Time 1 

5 kms/hr

 Let the speed of boat be x and speed of river be y.

 Speed upstream = x - y
Speed downstream = x + y

 Also x - y +5 = x + y.
 So y = 2.5 kms/hr

and 3(x - y) = x + y
 -> 3x - 3y = x + y
 -> 2x = 4y
 -> x= 2y = 5kms/hr

Students in a Row - Answer

View the Question Students in a Row

 

10
It can be seen as:

10 students - Rohan - 10 students - Anuj - 8 students 

Total students = 30 

Collision of Trains - Answer

View the question Collision of Trains

 

160kms
Since the distance of trains from each other is 200 km, and their relative speed is 120 + 80 = 200km/hr, therefore, the trains will collide in 1hr. This means that the bug also flies for 1 hr at an speed of 160hm/hr, and covers a distance of 160kms.

Number Series - Answer

View the Question on Number Series

 

Answer (i)

0, 2, 24, 324, ____

0 = 0¹ x 1,
2 = 1² x 2,
24 = 2³ x 3,
324 = 3⁴ x 4,

So the next term = 4⁵ x 5 = 5120

Answer (ii)

1, 8, 9, 64, 25, 216, ____

This is a mixture of 2 series.
1² = 1,
2³ = 8
3² = 9,
4³ = 64,
5²= 25,
6³ = 216,

So the next term = 7² = 49

Brainteaser 1 - Answer

Check out the Brainteaser 
 

Light one of the threads from 1 end, while light the other thread from both ends. The second thread will burn completely after 1/2 hr or 30 minutes. At this time, the first thread has also burnt for 30mins. Now light it from both ends. It would also begin to burn at double speed, and will last for another 30/2 or 15 minutes. So total time measured will be 30 + 15 or 45 minutes.