PUZZLES

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115. MERCHANT VESSEL

Captain of the merchant vessel M.V. Cougar Ace asked the duty officer Manpreet Singh Luthara, ‘What is the date today?’ The officer replied ‘Sir, it is 21st March’. After 10 minutes, captain asked again ‘What is the date today, Manpreet?’ The officer replied, ‘Sir, it is 23rd March’. How is this possible?

116. TWO COINS

Two five rupee coins were placed on the top of a frictionless slope and left to go down by gravitational force. One of them was kept with the curved surface (edge wise) touching the slope while the other one with face of the coin (flat wise) touching the slope. Which coin would reach the bottom of the slope first?

117. SWIMMING AND DANCING

When the number of students in Modern High School has increased, the school administration made two sections in class VIII, because there could not be more than 100 students in a section. If 1/11th of section A, and 1/7th of section B know swimming and 1/9th of section A and 1/13th of section B know dancing, can you say total how many students of class VIII know dancing? What is the total strength of class VIII students?

118. DIRECTION DILEMMA

Yashwant Kumar was a pilot on a fighter jet. He started moving in north direction when after sometime he took two turns, first towards left followed by right. Now he found his compass showing him moving in south direction. Control Room confirmed his direction as south-ward. Try and Explain.

119. TRUCK ON A BRIDGE

An empty truck was moving on a country road that had a bridge covered from top. The height of the bridge was just about 0.5 cm. less than that of the truck roof. Buddhadeb, an intelligent driver, thought of removing some air from each tyre of the truck thinking that its height would reduce but unfortunately he could not do it as the valve was too tight to rotate. Can you help him to cross the road?

120. ARMY PARADE

During an army parade, the camp Captain told the instructor to arrange 12 cadets in such a way that there should be six rows with each row containing four cadets and the arrangement should be symmetrical from all the sides. How will the instructor do?

ANSWERS:

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115. MERCHANT VESSEL

Welcome to the world of marine, where we have some different and amusing rules. Every time when a ship travels from one country to another, it has to set its clock to match with the local time. But when it crosses the International Date Line, a complete change of date occurs. Captain asked the officer around 23.50 hrs when the ship was just to the east of the Date line. That imaginary line goes across the middle of the Pacific Ocean. They sailed in the western direction and passed the date line. So it became 22nd March. As 10 minutes later, it was already 24.00 hrs and it became 23rd. So, certainly there was an increase of two days.

116. TWO COINS

The height from which the coins were sliding down was the same for both the coins and as there was no friction, so the total kinetic energy they achieved would be same for both. Kinetic energy of sliding coin is given by ½mv². But, that for a rolling coin, it constitutes two parts - one of that is rotational kinetic energy and another is linear kinetic energy. So, the actual speed with which rolling coin would come down would be lesser than that of the sliding coin and hence the sliding coin would come first.

117. SWIMMING AND DANCING

Consider section A and B separately. 1/11th of section A know swimming and 1/9th know dancing, so the strength of this section must be a multiple of the LCM of 11 and 9. We know that LCM of 11 and 9 is 99, and the strength of a section could not be more than 100, so strength of section A had to be 99 out of which 9 students know swimming while 11 students know dancing. Similarly, for section B total strength was 13 x 7=91, out of that 13 students know swimming and 7 students know dancing. So, total number of students who know dancing is 11+7=18, and total strength of class VIII was 99+91=190.

118. DIRECTION DILEMMA

What if Yashwant crosses above the North Pole?

119. TRUCK ON A BRIDGE

The only way to pass the bridge is to put some weights on the truck such that its tyres get pressed down and the effective height of the truck will be reduced.

120. ARMY PARADE

There are twelve cadets and six rows each containing four cadets, 6 x 4=24. So, each cadet should be counted in two rows. So the arrangement should be something like this. Here the circles show the positions of the cadets.

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