Questions tagged [mental-math]

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3
votes
1answer
583 views

Determining the first digit of the Quotient using hand long division efficiently?

For instance in the following problem: _____ 48)4368 To determine an initial 9 for the first number in the Quotient, you ...
4
votes
2answers
187 views

What's the word for addition and subtraction without borrowing or carrying over?

Is it regrouping? Upon googling it seems regrouping is borrowing or carrying over collectively. What's the word for not borrowing and carrying over? It's supposedly to train mental computation. ...
19
votes
16answers
3k views

Tricks for computing things in your head

There are quite a lot of tricks/shortcuts enabling doing calculations efficiently in your head. (One of them that came to me today is the "squaring a number ending with a 5" trick I wrote about in ...