Mathematics Stack Exchange
Mathematics Stack Exchange

Questions tagged [mental-arithmetic]

Mental arithmetic comprises arithmetical calculations using only the human brain, with no help from calculators, computers, or pen and paper.

Mental arithmetic comprises arithmetical calculations using only the human brain, with no help from calculators, computers, or pen and paper.

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Sum of values from 1 to 100 excluding values with digits of 7 and/or 8

I want to quickly sum values from 1 to 100, but exclude values with digits of 7 and/or 8 (e.g., 7,8,17,18,70,78,....) from the sum. This is a mental math problem that I want to do in a really quick way. The fastest approach I could come up with is…
24n8
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I want to learn math do I need to memorise the times tables?

As a front end developer, I do not need Math, however, I want to seriously learn it so that, maybe, one day, I might be able to get so good at it as to get into AI. I started with Algebra 1 and quickly realized I needed to brush up on pre-algebra. I…
relidon
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Generating "random" mental calculation exercises?

I recently tried to come up with "random" mental calculation exercises in an attempt to fight traffic jam boredom. Unfortunately, I quickly got bored by the lack of creativity of the problems I can generate for myself. My question is: Are there any…
bluenote10
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Multiplication tables: up to what number should I memorise?

I never memorised them and suffered immensely through school as a result. Eg. I calculated 7x8 as (7x10=70) minus 7 using my fingers (63) then minus again on my fingers (56). In Australia children are encouraged to memorise multiplication up to 12…
Humanities Guy
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Without using a calculator how to solve $x^x = 100$?

Without using a calculator how to solve $x^x = 100$ ? A way of finding an approximation to 2 decimals would be good neough. I know about the Lmabert W function but one cannot compute it mentally. This is why I believe my question not to be a…
astudentofmaths
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Problems on Trains

A train Leaves station $x$ at $5 AM$ and reaches station $y$ at $9AM$. Another train leaves station $y$ at $7AM$ and reaches station $x$ at $10.30 AM$ . At what time do the two trains cross each other? I have tried: Let the trains cover the (same)…
cloud computing in salesforce
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