On the math portion of the SAT, it is important to remember the basics about math and divisibility rules. The more that is known, the easier the math section of the SAT will be. To help brush up basic math skills, we are going to take a look at divisibility rules and how they apply to the SAT math section.
If …. / It is divisible by …
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A number is even - It is divisible 2
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The sum of the digits is a multiple of 3 - It is divisible by 3
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The last two digits are divisible by 4 - - It is divisible by 4
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A number ends in 5 or 0 - It is divisible by 5
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The sum is a multiple of 3 and it is an even number - It is divisible by 6
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The sum of the last three numbers are divisible by 8 - The entire number is divisible by 8
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The sum of the numbers is a multiple of 9 - The number is divisible by 9
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The number ends in zero - The number is divisible by 10
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The number is divisible by both 3 and 4 - The number is divisible by 12
TIP: Learning to use cross-canceling, decimal equivalents, common fractions and other methods are wonderful ways to help on the SAT math section. However, when a short cut it not possible, it is advisable to do the work on a calculator. Sometimes it is tempting to do the math by hand, but on the SAT only one thing matters - the final score. Those who worry about "showing off" by doing math by hand take a bigger chance of getting a lower overall score on the math section of the SAT. This is not a test about having fun or showing off math skills. When doing basic math, it is important to use all the tools available to get the best score.
Remainders and Patterns
When using remainders on the SAT, it is important to remember the basics about remainders. When using a calculator, it can sometimes be tricky. Occasionally, the SAT will ask for an answer in the 13 R 2 variety where R is remainder. When doing long division by hand this is easy to achieve, but sometimes calculators can remove a step giving the wrong type of answer.
TIP: When an SAT math question asks for the remainder, they are looking for a whole number that is left over - not a decimal or a fraction. Sometimes, a tricky question will arise that asks what a number used in a division problem was. Knowing techniques to answer these questions will dramatically increase the chances of a higher score on the math portion of the SAT.
BONUS TIP: Another tricky type of question on the SAT gives the remainder and asks for a number originally used in the division problem.
Example Questions:
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What is the remainder of 14551 when it is divided by 31?
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What is the 105th letter in the repeating sequence: B, C, D, E, F, G...
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For the sequence of numbers: 1, -2, 3, -4, 5, -6, 1, -2, 3, -4, 5, -6, … what is the sum of the first 50 numbers in the sequence?
Remainder questions on the SAT became very common after they started allowing calculators for the SAT math section. They are a simple math concept, but they are easily used in creating questions for the math portion of the SAT that are difficult, confusing and very challenging.
