Prime numbers are like the Lego bricks of number theory, and if you’re a real math nerd you know you love number theory. But wading your way through a sea of composite numbers looking for those magic numbers at either end of the scale, either the noble primes themselves or those composite numbers with who have a really interesting family tree of primes that multiply out to their true quantitative majesty…

So, what every number explorer needs is a prime factorization calculator, and I just built a really fun one here. It’s animated. And in color. And perfect for playing with numbers in the classroom, on your Smart Board or just whenever you’ve got a number that seems like it’s got an interesting prime pedigree…

Prime factorizations are a great tool for figuring out greatest common divisors (or largest common denominators if that’s how you swing), or for finding the least common multiple. But naturally, this calculator will tell you quite promptly if a number is prime as well.

Give it a try and see what you can discover about your own favorite number. It’s factor tree may actually surprise you…

The poor countdown timer here at DadsWorksheets has been neglected for some time, and with the site having gone through some significant technology upgrades, the timer became something of an orphan child, replete with scars and an inferiority complex, you know that one you keep in the closet and hope that at some point it’s just going to have an owl swoop in with an engraved invitation to go off to magic timer school where it saves the world or something.

After waiting somewhat impatiently for ANY sort of feathered visitor, I had to take matters more into my own hands, and a few thousand lines of JavaScript incantation later, I’m pleased to share with you the new countdown timer…

You don’t need to invoke specialis revelio to see this is a wizardly improvement over the old timer. Obliviously one big change is the circular timer graph, which provides immediate feedback about how far along the timer has progressed. It also lets you trigger sounds when the timer reaches the halfway mark or nears the end of the time you assign, and there are preset buttons like “Set Timer for 10 Minutes” and similar amounts that let you very quickly configure the timer for frequently used times.

As with the previous timer, you can save a URL that has all of your specific settings so that it’s easy to return to a timer ready to go.

While we’re using this as a timer for math tests and worksheets, it’s perfect for anything where you need a countdown. Use it as a classroom timer, a recipe timer or to keep track how long that pectrificus totalus is going last.

Percentages are an important part of both math and daily life. We deal with percentages all over the place… Calculating tips, 50% off sales, sales tax, or (dare I mention it in April?) income taxes. All of these areas work with percentages.

This percentage calculator easily allows you to convert a percent to fraction or, in reverse, a fraction to percent. By playing with the various values, you can work out various types of problems (“what percent of a number is some other number” for example), and the spoken-word version of various types of problems is shown in the preview. Working various problems through the calculator will quickly build experience with various types of percentage problems.

Also be sure to check out the various fraction and percentage math worksheets on the site for more practice.