
Sum of digits of 1999^1999 Recursively reduced to 1 digit
Answer: 1
1999^1999 = A pretty big number, so calculating this and doing is not the way.
1999 = 1998 + 1
Now all numbers with (9k+1)^n = 9M+1
Therefore 1999^1999 = …

MMXI in Google Logo
I = 1
V = 5
X = 10
L = 50
C = 100
D = 500
M = 1000
It's not L... That letter is I
M + M + …

Measure 4 litre of water using a 3 litre jar and a 5 litre jar
Solution 1
 Fill the 3 liter jar and pour it into the 5 liter jar.
 Do it again,
 Now in the 3 liter jar you will be left with one litre.
 Throw …

10 cricket balls one is heavier or lighter. Find the ball in 3 weighing chances.
Lets name the balls 0 1 2 3 4 5 6 7 8 9 for convinience.
Step 1 : Take 3 balls from this set lets take 0 1 2 and weigh …

Find the number of zero's in 'Factorial of a number' N factorial
For n as the number,
round(n/5) + round(n/25) + round(n/125)+.......+round(n/5^n)
etc till the reminder is 0.
Explain how?
A zero is formed when a 5 and 2 get multiplied, therefore finding the …

Select second largest value in a column using SQL
The answer is pretty simple without jumping over hoops or thinking about taking MAX etc.
SELECT value FROM table ORDER BY value DESC LIMIT 1,1
Why LIMIT 1,1 ? Shouldnt it be …

Create 24 using Addition Subtraction Multiplication and Division from 3 3 8 8
8 / (3  8 / 3) = 24

Reminder after dividing factorial 1! + 2! + 3! + ? + 100! By 7?
(a + b + c + d + .... x ) / 7 = a/7 + b/7 + c/7 + .... x / 7
Therefore 1!+2!+..100! / 7 = 1!/7 + .. …

Measure 30 Minutes and 15 minutes with a 20 Minute Candle
To measure 30 minutes, first of all light one candle at both the ends, now the time taken by the candle to burn is 10 minute. Then light the second candle and …

Combinations to Reach Nth Stair by moving up one step or two step at a time.
The answer to this can be found out by induction.
To reach the N^{th} Stair, we can reach by jumping one step from the (N  1)^{th} stair or jumping …

Number of Tennis Balls to make a 4 sided pyramid of 25 levels
Answer : 5525 Balls
Start from the top of the pyramid.
For a pyramid of 1 level  Number of Tennis balls required is 1
For a pyramid of 2 level  …

Divide A Triange into a 5 triangle of equal Area.
The answer is pretty simple and straight forward.
Area of a triangle is 1/2 x (base) x (height).
So divide the base into 5 segments and join the segment end points to …

Jar of Oranges Apple and Mix of oranges and apple
Answer : 1 Fruit
The point to be noted here is that the labels of the jar are all mislabeled, that means the labels always lie. Now suppose we have the 3 …