ISEE Upper Level Quantitative : Numbers and Operations

Study concepts, example questions & explanations for ISEE Upper Level Quantitative

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Example Questions

Example Question #11 : Other Factors / Multiples

What is the prime factorization of \displaystyle 16ab^2?

Possible Answers:

\displaystyle 2\cdot 2\cdot 2\cdot 2\cdot 2\cdot a\cdot b\cdot b

\displaystyle 2\cdot 2\cdot 2\cdot a\cdot b\cdot b

\displaystyle 2\cdot 2\cdot 2\cdot 2\cdot a\cdot b

\displaystyle 2\cdot 2\cdot 2\cdot 2

\displaystyle 2\cdot 2\cdot 2\cdot 2\cdot a\cdot b\cdot b

Correct answer:

\displaystyle 2\cdot 2\cdot 2\cdot 2\cdot a\cdot b\cdot b

Explanation:

First make a factor tree for 16. Keep breaking it down until you get all prime numbers (for example: \displaystyle 4\times 4, which then yields \displaystyle 2\times 2\times 2\times 2). Then, at the end, remember to factor the variables as well. Since the b term is squared, that means there are two of them. Therefore, the final answer is \displaystyle 2\cdot 2\cdot 2\cdot 2\cdot a\cdot b\cdot b.

Example Question #12 : Other Factors / Multiples

Which one is greater?

 

\displaystyle (a) number of factors of \displaystyle 100

\displaystyle (b)\ 10

Possible Answers:

\displaystyle (a) and \displaystyle (b) are equal

 

it is not possible to tell based on the information given.

\displaystyle (b) is greater

\displaystyle (a) is greater

Correct answer:

\displaystyle (b) is greater

Explanation:

Factors of \displaystyle 100 are:

 

\displaystyle 1,2,4,5,10,20,25,50\ and\ 100. So it has \displaystyle 9 factors which is less than \displaystyle 10.

 

Example Question #13 : Other Factors / Multiples

Which one is greater?

 

\displaystyle (a) The sum of all of the factors of \displaystyle 72

\displaystyle (b)\ 200

 

Possible Answers:

\displaystyle (a) and \displaystyle (b) are equal

\displaystyle (a) is greater

\displaystyle (b) is greater

it is not possible to tell based on the information given.

Correct answer:

\displaystyle (b) is greater

Explanation:

Factors of \displaystyle 72 are:

 

\displaystyle 1,2,3,4,6,8,9,12,18,24,36\ and\ 72. So we can write:

 

\displaystyle 1+2+3+4+6+8+9+12+18+24+36+72=195

 

Example Question #14 : Other Factors / Multiples

Which one is greater?

 

\displaystyle (a) The number of factors of \displaystyle 289

\displaystyle (b) The number of factors of \displaystyle 361

Possible Answers:

\displaystyle (a) and \displaystyle (b) are equal

It is not possible to tell based on the information given.

\displaystyle (a) is greater

\displaystyle (b) is greater

Correct answer:

\displaystyle (a) and \displaystyle (b) are equal

Explanation:

\displaystyle 289 has only three factors of \displaystyle 1,17\ and\ 289

 

and

 

\displaystyle 361 also has three factors of \displaystyle 1,19\ and\ 361

 

So the number of their factors are the same

Example Question #15 : Other Factors / Multiples

Which one is greater?

 

\displaystyle (a) The number of factors of \displaystyle 80

\displaystyle (b) The number of factors of \displaystyle 70

Possible Answers:

\displaystyle (b) is greater

It is not possible to tell based on the information given.

\displaystyle (a) and \displaystyle (b) are equal

\displaystyle (a) is greater

Correct answer:

\displaystyle (a) is greater

Explanation:

The factors of \displaystyle 80 are \displaystyle 1,2,4,5,8,10,16,20,40\ and\ 80. So \displaystyle 80 has ten factors.

 

The factors of \displaystyle 70 are \displaystyle 1,2,5,7,10,14,35\ and\ 70. So \displaystyle 70 has eight factors.

 

So \displaystyle (a) is greater than \displaystyle (b).

Example Question #16 : Other Factors / Multiples

If we consider the factors of \displaystyle 169 as a set of numbers, compare the mean and the median of the set.

Possible Answers:

It is not possible to tell based on the information given.

The mean is greater

The median is greater

The mean and the median are equal

Correct answer:

The mean is greater

Explanation:

Factors of \displaystyle 169 are \displaystyle 1,13\ and\ 169. So we should compare the mean and the median of the following set of numbers:

 

\displaystyle \left \{ 1,13,169\right \}

 

The mean of a set of data is given by the sum of the data, divided by the total number of values in the set:

 

\displaystyle Mean=\frac{1+13+169}{3}=61

 

The median is the middle value of a set of data containing an odd number of values which is \displaystyle 13 in this problem. So the mean is greater than the median.

Example Question #17 : Other Factors / Multiples

If we consider the factors of \displaystyle 24 as a set of numbers, compare the mean and the range of the set.

Possible Answers:

The mean and the range are equal

The mean is greater

The range is greater

It is not possible to tell based on the information given.

Correct answer:

The range is greater

Explanation:

Factors of \displaystyle 24 are \displaystyle 1,2,3,4,6,8,12\ and\ 24. So we should compare the median and the range of the following set of numbers:

 

\displaystyle \left \{ 1,2,3,4,6,8,12,24\right \}

 

The range is the difference between the lowest and the highest values. So we have:

 

\displaystyle Range=24-1=23

 

The mean of a set of data is given by the sum of the data, divided by the total number of values in the set.

 

\displaystyle Mean=\frac{1+2+3+4+6+8+12+24}{8}=7.5

 

So the range is greater than the mean.

 

Example Question #18 : Other Factors / Multiples

If we consider the factors of \displaystyle 72 as a set of numbers, compare the median and the range of the set.

Possible Answers:

It is not possible to tell based on the information given.

The range is greater

The range and the median are equal

The median is greater

Correct answer:

The range is greater

Explanation:

Factors of \displaystyle 72 are \displaystyle 1,2,3,4,6,8,9,12,18,24,36\ and\ 72. So we should compare the median and the range of the following set of numbers:

 

\displaystyle \left \{ 1,2,3,4,6,8,9,12,18,24,36,72\right \}

 

The range is the difference between the lowest and the highest values. So we have:

 

\displaystyle Range=72-1=71

 

The median is the average of the two middle values of a set of data with an even number of values:

 

\displaystyle Median=\frac{8+9}{2}=8.5

 

So the range is greater than the median.

Example Question #19 : Other Factors / Multiples

Which one is greater?

 

\displaystyle (a) The sum of the factors of \displaystyle 24

\displaystyle (b) The sum of the factors of \displaystyle 28

Possible Answers:

\displaystyle (a) and \displaystyle (b) are equal

\displaystyle (b) is greater

\displaystyle (a) is greater

It is not possible to tell based on the information given.

Correct answer:

\displaystyle (a) is greater

Explanation:

Factors of \displaystyle 24 are: \displaystyle 1,2,3,4,6,8,12 \ and\ 24

\displaystyle \Rightarrow Sum\ of\ the \ factors=1+2+3+4+6+8+12+24=60

 

Factors of \displaystyle 28 are: \displaystyle 1,2,4,7,14\ and\ 28

\displaystyle \Rightarrow Sum \ of\ the\ factors=1+2+4+7+14+28=56

 

So \displaystyle (a) is greater than \displaystyle (b)

Example Question #21 : Other Factors / Multiples

If we consider the factors of \displaystyle 45 as a set of numbers, which one is greater?

 

\displaystyle (a) The range of the set

\displaystyle (b) Sum of the median and the mean of the set

Possible Answers:

\displaystyle (b) is greater

It is not possible to tell based on the information given.

\displaystyle (a) is greater

\displaystyle (a) and \displaystyle (b) are equal

Correct answer:

\displaystyle (a) is greater

Explanation:

Factors of \displaystyle 45 are \displaystyle 1,3,5,9,15\ and\ 45. So we have:

 

\displaystyle \left \{ 1,3,5,9,15,45\right \}

 

The range is the difference between the lowest and the highest values. So we have:

 

\displaystyle Range=45-1=44

 

The mean of a set of data is given by the sum of the data, divided by the total number of values in the set.

 

\displaystyle Mean=\frac{1+3+5+9+15+45}{6}=13

 

The median is the average of the two middle values of a set of data with an even number of values:

 

\displaystyle Median=\frac{5+9}{2}=7

 

 

So we have:

 

\displaystyle Mean+Median=13+7=20

 

So \displaystyle (a) is greater than \displaystyle (b)

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