6 ACT Math Formulas You MUST KNOW

In this video, Magoosh's ACT expert Kristin Fracchia goes over the six math formulas that you absolutely have to know for the ACT! Unlike the SAT, the ACT does not give you a list of formulas at the beginning of the math test. That means there are some you absolutely need to have memorized. Here are the more common ones that you might be called upon to use that you should definitely know by heart.

00:00 - Kristin introduces ACT math formulas
00:28 - Averages
01:38 - Slope
03:00 - Circumference of a circle / area of a circle
04:00 - Volume of a cylinder
04:41 - SOH - CAH - TOA

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[lindaduong]

Formulas:
sum = average * (number of things)
slope = (y2-y1)/(x2-x1)
y=mx+b
circumference = 2pir
area = pir^2
volume of cylinder = hpir^2
SOH CAH TOA
3-4-5 triangle

[livlife]

If your allowed to use a graphing calculator you can go into program and make notes and write down the equations

[GillAgainsIsland]

You left out a whole bunch of important ones. But it was better than nothing. Here's one they must know: the equation of a circle: (x-h)^2 + (y-K)^2 = r^2, where (h, k) are the coordinates of the center point.

[isabellalove]

If school was this simple I wouldn't have a hard time staying in school for explaining a topic over and over for so many days.

[halnic]

I'm watching this before I go to take my test. Thank you so much!

[SilverMiraii]

One important formula I use all the time

old quantity/100 = new quantity/x, where x will give you the percentage change
and of course you can substitute anything in any place of this equation and you'll get the answer for what you're solving, maybe you wanna find the new quantity given a percentage change

500/100 = x/20 x here will give you 20 percent from 500
equivalent to 500*0.2

Here's another useful thing, SOH CAH TOA, it's a mnemonic for remembering basic trig identities sin cos and tan.

And the way I remember the circumference of a circle is by the definition of pi.
pi is defined to be the circumference divided by the diameter c/d=pi, and with simple algebra you can get it in any form.

[thinkvibrant]

This was great! Thanks for sharing ways to remember also the volume of a sphere is probably worth memorizing!

[monsoon]

I took my ACT today and none of these formulas came

[inmyopinion]

Most kids that score poorly but have high GPAs is just lack of study time. Alot of kids won't put the 80 to 100 hours prep time in.

[thatchickhannah]

I wish you would run through and do an example problem :( I still don’t understand anything

[haleymarie]

With slope does it matter if you have x2-X1 over y2-y1?

[undeadman]

For area, just think squarea. Easy peasy, one and done.

[wormzz]

I’m taking the act tomorrow some of these I didn’t learn pray for me