Dr. Neale simply beautifully nudges, gently encourages mathematics olympiad students to learn to think further on their own…

Mathematics demystified

April 25, 2018 – 12:51 pm

Dr. Neale simply beautifully nudges, gently encourages mathematics olympiad students to learn to think further on their own…

November 18, 2017 – 11:34 am

**Reference:**

**Geometric Inequalities, Vol 12, Mathematical Olympiad Series, Gangsong Leng, translated by Yongming Liu, East China Normal University Press, World Scientific.**

“God is always doing geometry”, said Plato. But, the deep investigation and extensive attention to geometric inequalities as an independent field is a matter of modern times.

Many geometric inequalities are not only typical examples of mathematical beauty but also tools for applications as well. The well known Brunn-Minkowski’s inequality is such an example. “It is like a large octopus, whose tentacles stretches out into almost every field of mathematics. It has not only relation with advanced mathematics such as the Hodge index theorem in algebraic geometry, but also plays an important role in applied subjects such as stereology, statistical mechanics and information theory.”

ðŸ™‚ ðŸ™‚ ðŸ™‚

Amazon India link:

May 3, 2017 – 11:24 pm

The animals may have gone into Noah’s Ark two by two, but in which order did they go in? Given the following sentence (yes, sentence! — I make no apologies for the punctuation), what was the order in which the animals entered the Ark?

The monkeys went in before the sheep, swans, chickens, peacocks, geese, penguins and spiders, but went in after the horses, badgers, squirrels and tigers, the latter of which went in before the horses, the penguins, the rabbits, the pigs, the donkeys, the snakes and the mice, but the mice went before the leopards, the leopards before the squirrels, the squirrels before the chickens, the chickens before the penguins, spiders, sheep, geese and the peacocks, the peacocks before the geese and the penguins, the penguins before the spiders and after the geese and the horses, the horses before the donkeys, the chickens and the leopards, the leopards after the foxes and the ducks, the ducks before the goats, swans, doves, foxes and badgers before the chickens, horses, squirrels and swans and after the lions, tigers, foxes, squirrels and ducks, the ducks after the lions, elephants, rabbits and otters, the otters before the elephants, tigers, chickens and beavers, the beavers after the elephants, the elephants before the lions, the lions before the tigers, the sheep before the peacocks, the swans before the chickens, the pigs before the snakes, the snakes before the foxes, the pigs after the rabbits, goats, tigers and doves, the doves before the chickens, horses, goats, donkeys and snakes, the snakes after the goats, and the donkeys before the mice and the squirrels.

ðŸ™‚ ðŸ™‚ ðŸ™‚

Nalin Pithwa.

May 2, 2017 – 12:10 am

April 29, 2017 – 11:42 pm

https://madhavamathcompetition.com/

Mathematics Hothouse.

April 20, 2017 – 12:10 pm

Just as you go to the gym daily and increase your physical stamina, so also, you should go to the “mental gym” of solving hard math or logical puzzles daily to increase your mental stamina. You should start with a laser-like focus (or, concentrate like Shiva’s third eye, as is famous in Hindu mythology/scriptures!!) for 15-30 min daily and sustain that pace for a month at least. *Give yourself a chance.* Start with the following:

The logicalympics take place every year in a very quiet setting so that the competitors can concentrate on their events — not so much the events themselves, but the results. At the logicalympics every event ends in a tie so that no one goes home disappointed ðŸ™‚ There were five entries in the room, so they held five races in order that each competitor could win, and so that each competitor could also take his/her turn in 2nd, 3rd, 4th, and 5th place. The final results showed that each competitor had duly taken taken their turn in finishing in each of the five positions. Given the following information, what were the results of each of the five races?

The five competitors were A, B, C, D and E. C didn’t win the fourth race. In the first race A finished before C who in turn finished after B. A finished in a better position in the fourth race than in the second race. E didn’t win the second race. E finished two places Â behind C in the first race. D lost the fourth race. A finished ahead of B in the fourth race, but B finished before A and C in the third race. A had already finished before C in the second race who in turn finished after B again. B was not first in the first race and D was not last. D finished in a better position in the second race than in the first race and finished before B. A wasn’t second in the second race and also finished before B.

*So, is your brain racing now to finish this puzzle?*

Cheers,

Nalin Pithwa.

PS: Many of the puzzles on my blog(s) are from famous literature/books/sources, but I would not like to reveal them as I feel that students gain the most when they really try these questions on their own rather than quickly give up and ask for help or look up solutions. Students have finally to stand on their own feet! (I do not claim creating these questions or puzzles; I am only a math tutor and sometimes, a tutor on the web.) I feel that even a “wrong” attempt is a “partial” attempt; if u can see where your own reasoning has failed, that is also partial success!

May 13, 2016 – 12:44 am

**Problem:**

Of all triangles with a given perimeter, find the one with maximum area.

**Solution:**

Consider an arbitrary triangle with side lengths a, b, c and perimeter . By Heron’s formula, its area F is given by

Now, the arithmetic mean geometric mean inequality gives

Therefore,

where inequality holds if and only if , that is, when .

Thus, the area of any triangle with perimeter 2s does not exceed and is equal to only for an equilateral triangle. QED.

More later,

Nalin Pithwa

PS: Ref: Geometric Problems on Maxima and Minima by Titu Andreescu et al.

February 13, 2016 – 11:27 am

**Reference: Combinatorial Techniques by Sharad Sane, Hindustan Book Agency.**

**Theorem:Â **

The inclusion-exclusion principle: Let X be a finite set and let and let Â be a set of n properties satisfied by (s0me of) the elements of X. Let denote the set of those elements of X that satisfy the property . Then, the size of the set of all those elements that do not satisfy any one of these properties is given by

.

**Proof:**

The proof will show Â that every object in the set X is counted the same number of times on both the sides. Suppose and assume that x is an element of the set on the left hand side of above equation. Then, x has none of the properties . We need to show that in this case, x is counted only once on the right hand side. This is obvious since x is not in any of the and . Thus, X is counted only once in the first summand and is not counted in any other summand since for all i. Now let x have k properties say , , , (and no Â others). Then x is counted once in X. In the next sum, x occurs times and so on. Thus, on the right hand side, x is counted precisely,

times. Using the binomial theorem, this sum is which is 0 and hence, x is not counted on the right hand side. This completes the proof. QED.

More later,

Nalin Pithwa

December 30, 2015 – 4:26 pm

**Exercise XXVII. Problem 30.**

If a, b, c are in AP, prove that , , are in AP.

**Proof:**

Given that

TPT: **. —— Equation 1**

Let us try to utilize the following formulae:

which implies the following:

and

Our strategy will be reduce LHS and RHS of Equation IÂ to a common expression/value.

which is equal to

which is equal to

which is equal to

which in turn equals

From the above, consider only the expression, given below. We will see what it simplifies to:

—- **Equation II.**

Now, consider RHS of Equation I. Let us see if it also boils down to the above expression after simplification.

From equation II and above, what we want is given below:

that is, want to prove that

but, it is given that and hence, , which means and

that is, want to prove that

i.e., want:

i.e., want:

i.e., want:

Now, in the above,

.

Hence, .

**QED.**

October 11, 2015 – 7:39 am

**Question: Consider the function **

. Can you graph it? It is variable raised to variable. Send me your observations.

**Now, consider the functions:**

, ,

, .

Can you graph these? What is the difference between these and the earlier generalized case?

**Now, consider the function:**

Let .

Arrange ,

and

in decreasing order.

Kindly send your comments/observations.

More later,

Nalin Pithwa