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20 Cards in this Set
- Front
- Back
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When is an integer divisible by 2? |
If the integer is EVEN |
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When is an integer divisible by 3? |
If the sum of the integer's DIGITS is divisible by 3 |
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When is an integer divisible by 4? |
If the integer is divisible by 2 TWICE, or the LAST TWO digits are divisible by 4 |
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When is an integer divisible by 5? |
If the integer ends in 0 or 5 |
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When is an integer divisible by 6? |
If the integer is divisible by BOTH 2 and 3 |
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When is an integer divisible by 8? |
If the integer is divisible by 2 THREE TIMES, or if the last three digits are divisible by 8 |
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When is an integer divisible by 9? |
If the SUM of the integer's DIGITS is divisible by 9 |
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When is an integer divisible by 10? |
If the integer ends in 0 |
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What is the greatest common factor? How do you find it? |
The largest divisor of two or more integers. To find it: 1. Factor numbers into primes 2. Create a venn diagram 3. Place each common factor appearing more than once in the overlap 4. Place the remaining non common factors in the non shared areas 5. Take the product of primes in the overlapping region |
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What is the lowest common multiple? How do you find it? |
The smallest multiple of two or more integers. To find it: 1. Factor numbers into primes 2. Create a venn diagram 3. Place each common factor appearing more than once in the overlap 4. Place the remaining non common factors in the non shared areas 5. Take the product of all the primes in the diagram |
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What is the formula to remember for a remainder problem? |
The formula can be simplified to dividend = (quotient * divisor) + remainder. |
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Positive integers with only two factors must be ______ |
Prime, only 1 and itself |
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If you add or subtract a multiple of an integer what is true about the result? |
You get anther multiple of the integer. |
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If you add/subtract a multiple of N to a non multiple N what is true about the results? |
It's a non multiple of N |
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If you add/subtract two non multiples of N, what is true about the result? |
It could be either a multiple of N or a non multiple of N. |
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What are factor pairs? |
A table to find all factors (NOT just prime) for a number. Make a table to find. |
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How many factors does a perfect square and a non square have? |
Perfect square = Odd. Because one factor pair is duplicated. Non perfect = Even |
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For harder remainder problems what's a good strategy? e.g if x has a remainder of 3 when divided by 7 and y has a remainder of 2 when divided by 7, what is x+y divided by 7? |
Pick suitable numbers. 14 + 3 = 17 7+2= 9 17+9 = 26. dividing by 7 is 5. |
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How do you solve remainder problems with decimals?
e.g. When A is divided by B, the result is 4.35. What could a remainder be? |
Use the relationship decimal to find the integer value for a decimal. part = remainder/divisor
e.g. 0.35 so 7/20 = R/B so 7B = 20R. This means 7 is a factor of B and hence the remainder is a multiple of 7. |
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How do you get all the factors if you know the prime of a number? e.g. How many factors does 9450 have? |
If a number has the prime factors a^x * b^y * c^z then the number has (x+1)(y+1)(z+1) different factors. |
