# CTK Insights

• ## Pages

01 Apr

### Why Learn Mental Math Tricks?

I strongly believe that those tricks are more than anything else convey to the early learners the essence of practicing mathematics. Presh Talwalkar's book may also open the eyes of an older generation on what they missed in the early grades.

06 Jul

### Weather Forecasting: A Story of Mathematical Triumph

But naturally, mathematics was not evolving all by itself. The authors excel in presenting establishment of the science of meteorology as a human endeavor. The history of meteorology is rich in perseverance, sacrifice, enthusiasm, ingenuity, useful missteps, multinational collaboration ... and plain hard work. Authors' fluent recount makes the story all the more fascinating, even if math applications are only at the back of your mind. The book is a superior read.

14 Feb

### The Butterfly Effect

I realize that the book was shipped some time before the tweeter discussion has started; still, the thought that there might be a relation to the butterfly effect crossed my mind. On opening the book I almost immediately noticed a cartoon that did not immediately invoke any connection to weather prediction

19 Sep

### A Magical Incident due to the Paypal's Policy

I believe that the discrete variant makes the solution more transparent. For example, think of coffee and cream not as liquids but as collections of molecules. Since the number of molecules in the two glasses remains the same even after repeated iterations, cream molecules in the "water" glass come at the expenses of the water molecules in the "cream" glass and, therefore, the two quantities are equal.

02 Aug

### Evolution of a problem and an answer

TweetIn grades 1 through 5, my little boy went to a private Hebrew school. Every day I drove him there and then picked him up at the end of the day - half an hour drive each way. We spent the combined hour mostly talking of mathematics. For the next three years he took the […]

27 Jun

### Bags, Coins, and Questions

There are 31 bags placed in a row with 100 identical coins each. One bag is selected and one coin is moved from the selected bag to every bag to the right of it. A question can be asked for a total number of coins in any group of bags. How many questions are needed to determine the chosen bag?

16 Jun

### Weakly Refuted Story of Queen Victoria

TweetI like buying books, especially serendipitously. For the past year this was mostly by simply browsing the amazon.com Kindle store. Today after a long hiatus I bought a book in a bookstore of old ("conventional" may not be the right word anymore.) I've been taking a walk with my sister-in-law - a full-time Israeli, and […]

24 Feb

### Cartesian axes and parallel lines

I always feel apprehension on seeing the number line or x-axis introduced as a horizontal line, with the numbers increasing left to right. When the time comes, the y-axis is commonly introduced as perpendicular to the x-axis and hence vertical. Seldom there is enough time for a trifle observation that the direction of a number line is irrelevant and that the choice of the orientation of the system of axes in the plane is a matter of convenience. The trouble comes when there is a need to change variables or, say, introduce the inverse function.