Maria Zeltser - How to Calculate Like a Magician?

Most schoolchildren think that Mathematics is boring and complicated. When they need to calculate in their notebooks, or – god forbid – in front of the blackboard, it will take a lot of time and oftentimes leads to erroneous results. It turns out there is no need to go through all that trouble, says Associate Professor of Mathematics at the Tallinn University School of Digital Technologies, Maria Zeltser - reports on the site of Tallinn University.

Simple and elegant methods of calculating quickly have been discovered ages ago. Some of the easiest ways of calculating were discovered in India over 2500 years ago.

Let’s see how easy it can be. Say we need to multiply 112 and 107. They are both close to 100. Let’s take the number 100 as a basis and show the multipliers as: 112=100+12; 107=100+7. Let’s write down the calculation as:

112 + 12


107 + 7

To find the answer, we only need two parts. The right side of the answer is equal to the multiplication of the two numbers on the right: 12x7=84. The left side is to be calculated diagonally: 112+7=119. If we join the two sides, we get 11,984, which is the correct answer.

Note that the right side of the answer must have as many numbers as there are zeroes in the base number. For example, if we multiply 997 by 988, the basis is 1000 with three zeroes. The calculation looks like this:

997 – 3


988 – 12

The right side of the answer is -3x(-12)=36. As the base number had three zeroes, write it down as 036. The left side will be 997-12=985. Write down 985,036. Check it with your calculator – bingo!

The same method also works when one of the numbers is larger, and the other one is smaller than the base number. Let’s multiply 995 by 1012. The base number is still 1000.

995 – 5


1012 + 12

The right side is (-5)x12= -60, but as the base has three zeroes, let’s write it down as -060. The left side is 995+12=1007. How do we continue, when there’s a negative answer? We lend a ‘one’ from the left side (1007-1=1006), and calculate the right side as 1000-060=940. This adds up to 1,006,940.

Got it? Next time surprise your friends with your speed calculation abilities. After some practice, you’ll calculate faster in your head than it takes you to enter the numbers in your calculator.

Is mathematics boring and complicated? Certainly not!

Read other news on the city site of Tallinn.

Tallinn_University, calculate_like_a_Magician
If you notice an error, highlight the text you want and press Ctrl + Enter to report it to the editor
I recommend
No recommendations yet


Post your comment to communicate and discuss this article.

Chairman of the Estonian Chamber of Commerce and Industry and one of the owners of construction group Nordecon, Toomas Luman, finds that a prime ministerial candidate should first and foremost be able to answer the question of what will become of the demographic crisis in Estonia. The businessman sees controlled introduction of foreign labor as the solution. A digital construction cluster was created in Estonia a few years back to bring innovation to the s...
Last year saw 27,125 registered offenses, up 0.5 percent from the year before. Violent crime was up by 12 percent to 8,249 offenses. PHOTO: Dominic Lipinski / PA Wire / Press Association Images / Scanpix Growth was biggest for domestic violence – the police launched criminal proceedings in 3,607 cases that constitutes an increase of more than one-third – annual growth of 37 percent from 2,632 cases in 2017. At the same time, reports of domestic violence we...
TALLINN - Ahead of the withdrawal of the United Kingdom from the European Union, tens of thousands of British citizens have chosen the citizenship of some other country, but only one Brit has recently chosen an Estonian citizenship. Spokespeople for the Ministry of the Interior told BNS that only one British citizen submitted an application for Estonian citizenship last year and the applicant was also granted the citizenship. Before that, no Brits had soug...
TALLINN - Experts from Finland, Denmark, Norway and the Netherlands highlighted the importance of decentralization and granting local governments greater decision-making powers at a conference titled "Strong local government -- strong state?" in Tallinn on Wednesday.  All Nordic countries have chosen a model granting local governments significant decision-making powers, thus the central government does not prescribe how local governments are to fulfill the...
The language learning application Drops by game developer Planb Labs, established in Estonia by Hungarian founders, was named Google Play's best app of 2018. With the number of downloads surpassing 10 million, Drops was named Google's app of the year as the revenue of Planb Labs, a company registered in Estonia, increased fivefold, CNBC said. The developer's revenue grew from €335,000 in 2017 to €1.7 million in 2018. The company's shareholders include Hung...
TALLINN - The Estonian Health Board has banned the distribution of chlorine dioxide, also marketed as the Miracle Mineral Supplement (MMS), the A-component of an unused product, meaning the sodium chlorite solution, must be taken to a hazardous waste collection facility. Ester Opik, head of the Health Board's North regional department, said that the banning of the distribution of the product was caused by the fact that MMS, distributed as a cosmetics produ...
Nature cannot abide a vacancy, as the saying goes. If just one year ago, Estonia was battling the sale of MMS and the practice of giving it to children, a new “miracle cure” called Advanced TRS has appeared on the market now. Even though the make-up of the substance is different, the promise to cure autism and cleanse the body of heavy metals, which kind of extreme detox is accompanied by severe side-effects, sounds all too familiar. TRS is recommended to...
Allied NATO battalions will soon mark two years serving in the Baltics. They have worked better than expected but would need prepositioned heavy weaponry and a functional contingency plan in case of a crisis, a report by the International Center for Defense and Security (ICDS) finds. “We do not know how Russia would have acted had we not welcomed allies in Estonia, Latvia, Lithuania and Poland in 2017. I’m afraid they would have tested our resolve,” one of...
The time of filing income tax returns is nearly upon us. The new income tax system, in effect since last year, will obligate many women who went on maternity leave toward the end of the year to make additional income tax payments, while those who give birth in the middle or at the beginning of the year have no such obligation. What this means is that some women will owe the state simply for giving birth “at the wrong time”. Laura Roop, who went on maternit...