#11 - Hour Glass Puzzle

I have two sand hour glasses:
1. A 7 minute one and
2. An 11 minute one.

Using just these 2 sand hour glasses, how can i measure time as 15 minutes ?

Hour Glass Puzzle
View Answer Discuss

1. Start both the 7 minute hour glass & 11 minute hour glass.
2. Wait till the 7 minute hour glass times out. Time is 7 minute!
3. Restart the 7 minute hour glass. At this time 11 minute hour glass will have 4 minutes left to time out.
4. As soon as 11 minute glass times out invert the 7 minute hour glass. Total time now is 11 minutes.
5. After inverting 7 minute hour glass, it will now have 4 minutes left for time out.
6. After these 4 minutes times out, the total time is 15 minutes.

#12 - Mathematics Problem

I want to fill my bucket using both cold and hot water.
I have two taps for both cold and hot water. The hot water tap fills the bucket in exact 6 hours and cold water tap fills the bucket in exact 4 hours.
I turn both of them simultaneously but I forgot to turn off another tap which removes the water out of the bucket. This tap can empty the bucket in 12 hours.

How Long will it take to fill the bucket?

Mathematics Problem
View Answer Discuss

3 hours

Explanation :
(1/6 + 1/4 - 1/12) ^ (-1)
= (1/3)^(-1) = 3

#13 - Michael Phelps Maths Problem

Michael Phelps , the famous swimmer can swim downstream in a lake in exact 40 minutes (with the lake current helping time).
He can swim upstream in a lake in exact 60 minutes (against the lake current).
The length of lake is 2 kilometers.

How long Michael Phelps can cover distance of one side at a still lake (no current).

Michael Phelps Maths Problem
View Answer Discuss

48 minutes

#14 - Maths Puzzle Question

Two Twins Eddy and Roberto Baggio were standing back to back and suddenly they started running in opposite direction for 4 kilometers and then turn to left and run for another 3 kilometers.

what is the distance between the Baggio twins when they stop ?

Maths Puzzle Question
View Answer Discuss

10 kilometers

#15 - Horse Wind Puzzle

Emily learnt how to ride a horse recently. Just to test her skills, she rode the horse from her home till a mine which she covered in three minutes and returned back home from the same path only this time she took four minutes. The reason was that while riding away from home, she was supported by wind however while riding back, she was riding against the wind.

How fast do you think she could have rode a mile if there was no wind ?

Horse Wind Puzzle
View Answer Discuss

3 minutes and 25 5/7 seconds.

The most common way how most of people see this problem is adding 3 and four to obtain 7 and they believe it should give a correct average and thus her time should be taken to 3 and half minutes. But if you do like that, you will get to a wrong answer. This is because, the wind has only helped her for three minutes while it has worked against her for four minutes.
If she could ride a mile in three minutes with the wind, it is evident that she could go a mile and 1/3 of a mile in four minutes. Thus two and 1/3 miles in eight minutes will give her actual speed as the wind has helped her as much as it has worked against her.

Thus her actual time for a single mile without wind will be 3 minutes and 25 5/7 seconds.

#16 - Solve Mathematical Problem

There are two insects on a tile. Insect X is sitting on one side of the tile (point A) and Insect Y is sitting opposite on the other side of the tile (point B). Now both of them decide to change their position and thus X starts crawling to point B and Y starts crawling to point A. When they meet and pass each other in between, X takes 20 seconds to reach to B and Y takes just 5 seconds to reach A.

Can you calculate the total time each of the insects took to change their positions?

Solve Mathematical Problem
View Answer Discuss

Assume that P is the speed of Insect X and Q is the speed of Insect Y.
Let T be the number of seconds it takes them to cross paths.
Now Distance = Speed * Time

Thus for Insect X
Distance = P * T before meeting
And Distance = P *20 after meeting

For Insect Y
Distance = Q * T before meeting
And Distance = Q * 5 after meeting

Now the distance travelled by X before meeting is equal to the distance travelled by Y after meeting and vice versa

Thus
P * T = Q * 5
And Q * T = P * 20

Solving both equations, we get T = 10

Thus Insect X requires 10 + 20 = 30 seconds,
Whereas Insect Y requires 10 + 5 = 15 seconds to change the position.

#17 - Infosys Bridge Crossing Puzzle

A family is trapped in a jungle. There is a bridge which can lead them to safety. But at one time, the bridge can only allow two people to pass through. Also, all of them are afraid of the dark and thus, they can’t go alone.

Father takes 1 minute to cross, mother takes 2 minutes, son takes 4 and the daughter takes 5 minutes. While crossing the time taken will be according to the slower one. How can they all reach at the other side in the minimum possible time ?

Infosys Bridge Crossing Puzzle
View Answer Discuss

12 minutes
Father and Mother goes first: 2 minutes.
Father comes back: 2+1 = 3 minutes.
Both children go to mother: 3 + 5 = 8 minutes.
Mother comes back to Father: 8 + 2 = 10 minutes.
Mother and Father go: 10 + 2 = 12 minutes.

Thus, all of them reach the other sides in 12 minutes.

#18 - Solve My Math Problem

A costume party is going on in a class of a few students. The average of the boys (b) is g and the average age of the girls (g) is b. If the average age of all of them including their class teacher who is 42 years old is b+g.

Can you find the value of b+g?

Solve My Math Problem
View Answer Discuss

8

for b in range(1,99):
for g in range(1,99):
sum1=2*b*g+42
sum2=(b+g)*(b+g+1)
if(sum1==sum2):
print(b,g,sum1)

(b,g)=(3,5) => b + g=8

#19 - Distance Tyre Maths Problem

A man always keeps a spare tyre in his car. To make full use of all the five tyres, he changes the tyres in a manner that for a distance of 1, 00,000 km, each of them runs the same distance.

Can you calculate the distance traveled by each tyre in that journey ?

View Answer Discuss

80,000.

We need to calculate the 4/5th of the total distance to solve the problem.
4/5 * 1, 00,000 km = 80, 000 km

Thus, each tyre traveled 80, 000 km.

#20 - Distance Math Problem

There is a straight highway. Four different villages lie on that highway. The distance between them is different. The third village is 60km away from the first village; the fourth is 40 km away from the second; the third is 10 km near to the fourth that it is to the second.

Can you calculate the distance between the fourth and the first village ?

View Answer Discuss

75

First Village = A
Second Village = B
Third Village = C
Fourth Village = D

Distance between B and D = 40km
=> Distance between B and C + Distance between C and D = 40km
=> Distance between B and C + (Distance between B and C - 10) = 40 km
=> 2 * Distance between B and C = 50km
=> Distance between B and C = 25km

Therefore distance between C and D = 15km

Thus, distance between A and D = 60 + 15 = 75km