## Finding the Radius of a Sphere

(An archive question of the week) An interesting question came to us in 2016, where rather than using a well-known formula, it was necessary to work out both what data to use, and how to calculate the desired radius.

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# Checking

## Finding the Radius of a Sphere

## Challenging Rate Questions

## Avoiding “Stupid” Mistakes in Algebra

## Rounding: Contextual Issues

## Extraneous Solutions: Causes and Cures

## How Can I Stop Making Careless Mistakes?

## A Sample of Ask Dr. Math, Part 1: Questions from School

(An archive question of the week) An interesting question came to us in 2016, where rather than using a well-known formula, it was necessary to work out both what data to use, and how to calculate the desired radius.

(New question of the week) A conversation last week went through a number of interesting questions, starting with a couple on percentages, and moving into some that I would call rate questions. I will extract these, which I think will be useful for others. (The rest could, too, but there was just too much there …

(New Question of the Week) I like working with a student who is willing to take chances, and also willing to be corrected. As I have often explained, just like a medical doctor, a Math Doctor wants you to “show me where it hurts” in order to diagnose the problem; so showing detailed work is …

Previously, I discussed how to round a number to the nearest whole number [or tenth, ten, etc.]. I focused there on what to do when you are simply told to do it — what “round to nearest” means, and how that determines whether you round a particular number up or down. I also pointed out …

The other day a student I was helping face to face asked how she can know when to check for extraneous solutions of an equation. I gave her a quick version of my standard answer, and the light went on! Today I want to share these thoughts here, because they areĀ very important in several …

From time to time, a student will write to us asking for advice on studying, rather than on math itself. As either successful students, or teachers, or (quite often) as adults who recall overcoming difficulties in the past, we have some good advice to offer. Today, I want to look at three answers, by three …

In its more than 20 years, we answered hundreds of thousands of questions on Ask Dr. Math, only a small fraction of which were archived for public access. Those that did not make it into the archive were not bad answers, just not deemed to be of broad enough interest, or unique enough, to be …

A Sample of Ask Dr. Math, Part 1: Questions from SchoolRead More »