Tuesday 18 August 2015

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

Sunday 26 July 2015

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

Saturday 25 July 2015

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