#251 - Trick Math Problem

While boarding a bus you notice that there are 7 girls in the bus already. All the girls have 7 bags each. In each bag there are 7 adult cats. Each of the adult cat have 7 little one. Each of the cat has 4 legs.

Can you calculate the number of legs in the bus?

Trick Math Problem

Every girl has seven bags comprising of seven adult cats each with seven little cats per adult cat.
Thus for one girl:
1 girl + 49 adult cats + 343 little cats
Since there are 7 girls:
7 girls + 343 adult cats + 2410 little cats

Now calculating the legs:
14 legs of girls + 10976 legs of cats (There are total 2744 cats with 4 legs each).
Thus total legs = 10990

Now I climbed aboard the bus as well, thus total number of legs = 10990 + 2 = 10992 legs
If we add two legs of the driver as well,
Total legs = 10992 + 2 = 10994

#252 - Hard Maths Cube Riddle

You are given a cube that is made with the help of 10x10x10 smaller cubes summing up to a total of 1000 smaller cubes. You are asked to take off one layer of the cubes.

How many remain now?

Hard Maths Cube Riddle

512
A layer will mean to remove from all sides of the cube. Thus it would reduce the dimension be two not one. In this way only a cube of 8x8x8 will remain. This totals to be 512.

#253 - Fun Maths Riddle

There are four numbers given to you: 2, 3, 4 and 5. You are allowed to use only two mathematical symbols: + and = and come up with a mathematically true equation.

Can you do it?

PS- You can't repeat the symbols or numbers.

Fun Maths Riddle

3^2 = 4 + 5
(^ is used for squaring the term, it is not a mathematical symbol.)

#254 - Math Fraction Riddle

Arrange the numbers 1, 2, 3, 4, 5, 6, 7, 8 and 9 above and below the division line in a manner that the thus formed fractions equals to 1/3.

You can use one number only once.

Hint:
The numerator will have four digits and the denominator will have five digits.

Math Fraction Riddle

5832/17496
This fraction will result in 1/3.

#255 - Algebraic Equation Puzzle

Place a mathematical symbol between the numerals 5 and 9 in such a way that the resulting number is greater than 5 but smaller than 9.

Algebraic Equation Puzzle

If we place a decimal between the numbers it will become 5.9 which is what we needed.

#256 - Short Logic Maths Puzzle

Calculate the number of degree between the hour hand and the minute hand of an analogue clock that is displaying a time of 3:15 at present.

Short Logic Maths Puzzle

This question can be a bit tricky. But if you pay attention, you can solve it. When fifteen minutes have passed after three, the hour hand must have moved exactly one fourth of an hour. Thus both the hands will make an angle of 7.5 degree between them.

#257 - Logic Riddle For High School

Adam gave half of the apples he had plus one more to Eve. He gave half of the remaining ones plus one more to Diana. Now, Adam was left with just one apple.

Can you find out how many did he have in the beginning?

Logic Riddle For High School

10

In such type of questions we can come to a conclusion by working our way backwards.

He is left with one apple in the end. He gave half of what he had plus one to Diana. If we remove the extra one, the he must have had two apples. Since now both of them have half of the remaining ones, it must be 2 * 2 = 4 apples.

Again move back. Adam gave half of what he had plus one extra to Eve. Thus if we remove that extra one and give it back to Adam, then Adam must have 5 apples. Since he gave half to Eve, it means he must have had 5 * 2 = 10 apples in the beginning.

Thus Adam had 10 apples in the beginning.

#258 - Hardest Probability Problem

If you keep rolling a pair of dice together till a sum of 5 or 7 is obtained, then what is the probability that a sum of 5 comes before a sum of 7?

Hardest Probability Problem

This can be solved in a generic and complex way but let us not go into all that.

There can be four ways through which the pair of dice results in a sum of 5. There can be six ways through which the pair of dice can result in a sum of 7.

Now, we want the probability of the pair of dice resulting in a sum of 5 before a sum of 7. Thus probability = 4/(4+6) = 4/10 or 2/5.

#259 - Conditional Probabitlity Riddle Google Interview

A mathematics teacher took exam of his students. Out of the total students, 25% of the students passed both the tests included in the exam. However, only 42% were able to clear the first test.

Can you find out the percentage of those students who passes the first test and also passed the second test ?

60%

Explanation:
This type of questions call in for the application of conditional probability as the question is asking you to find out the probability that the second test was passed with the given situation that the first one was passed.

The formula for conditional probability:
P (Second/First) = P (First and Second)/ P (First)
= 0.25/0.42
=0.60
=60%

#260 - Popular Number Puzzle

You ask your friend to pick a random number and you have to make five guesses in order to find the number. You write all your guessed numbers on a paper and the differences between the guessed number and the picked number is written on another paper.

After that, one number is erased from each of the paper. Now there are only four numbers on each paper:

Guesses: 27, 32, 44, 45
Differences: 5, 7, 10, 13

Can you find out what is the number?

Popular Number Puzzle

37

The number is 37.
The missing guess can be either 24 or 50 and the missing difference is 8.