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# Tip #45 to Get a Top ACT Math Score

By Brian Leaf
McGraw-Hill Professional
Updated on Sep 7, 2011

"Careless errors are bad mmmkay." So, let's learn to avoid five more of the most common ones.

1. (x + 3)2 = (x + 3)(x + 3) = x2 + 6x + 9, not x2 + 9.
2. Remember the middle term when you FOIL.

3. 2(3)2 = 18, not 36.
4. Remember your old friend PEMDAS, order of operation.

5. Remember to finish the question. Sometimes you have gotten a number for part of a question and the ACT provides that number as an answer choice. So before you grid each answer, take a moment to pause and say, "Wait (insert your name here), did I finish the question?" This is so simple, but hugely important. This is the most common careless error, and it's so easy to avoid!
6. (x2)(4x5)(3x) = 12x8 not 12x7.
7. Remember that x without an exponent means x1.

8. Lots of ACT questions mention units, like feet or centimeters. And 90% of these are just there to make the question realistic and are not at all tricky. But when a question has feet and inches or hours and minutes in the same question, remember to convert correctly. For example, 3.5 feet is not 3 feet 5 inches; it is 3 feet 6 inches. And 2.5 hours is not 2 hours 50 minutes; it is 2 hours 30 minutes. Of course you know this, but it's easy to forget when rushing to solve a question. As long as you know to keep an eye out for it, you'll spot it when it comes up.

Students lose way too many points on careless errors. Don't do that. Memorize the above rules and practice watching for them. Be focused, relaxed, and mindful, and you will not make careless errors. You will be a math ninja, and like most ninja of ancient Japan, you will ace the ACT.

Let's look at this question:

Solution: Great question. So easy to make a careless error, unless you know to watch for it. To divide 9 feet 10 inches by 2, let's do feet and inches separately. Here's the key, 9 feet divided by 2 is 4'6", not 4'5", and 10 inches divided by 2 is 5". So 4'6" plus 5" equals 4'11". Nasty tricksy Hobbitses.

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