SAT Math : Fractions

Study concepts, example questions & explanations for SAT Math

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Example Questions

Example Question #1 : How To Find The Whole From The Part

A certain ball that is dropped will bounce back to 3/5 of the height it was initially dropped from.  If after the 2nd bounce the ball reaches  39.96 ft, what was the initial height the ball was dropped from? 

Possible Answers:

111 ft

100 ft

135 ft

150 ft

66 ft

Correct answer:

111 ft

Explanation:

We know the height of the initial bounce, so work backwards to find the initial height.  39.96/0.6 = 66.6 = height of ball after first bounce

66.6/0.6 = 111 ft

Example Question #1 : How To Find The Whole From The Part

A pitcher of water is filled \dpi{100} \small \frac{2}{5} of full.  An additional 27 ounces of water is added.  Now the pitcher of water is completely full.  How much water does the pitcher hold?

Possible Answers:

50

30

40

45

35

Correct answer:

45

Explanation:

If \dpi{100} \small 27 ounces fills the pitcher, then it must equal the volume of \dpi{100} \small \frac{3}{5} of the pitcher.  If \dpi{100} \small \frac{3}{5} of a pitcher equals 27 ounces, then \dpi{100} \small \frac{1}{5} of a pitcher equals \dpi{100} \small 27\div 3=9ounces.  Since there are \dpi{100} \small 5 fifths in the pitcher, it must hold \dpi{100} \small 9\times 5=45 ounces total.

Example Question #81 : Arithmetic

If Mr. Jones’ math class has 8 boys and two-thirds of the class are girls, how many total students are in the class?

 

Possible Answers:

Correct answer:

Explanation:

If two-thirds of the class are girls, then one-third must be boys. Set up an equation comparing the number of boys to how much they represent in the entire class:

8 = (1/3) x, where x is the number in the entire class.

When we solve for x in the equation we get x = 24.

 

 

Example Question #5 : How To Find The Whole From The Part

 is what  of what? 

Possible Answers:

Correct answer:

Explanation:

With the given information, we can set up a proportion. 

Example Question #1 : Decimals With Fractions

Find answer in simplified fraction form:

Possible Answers:

Correct answer:

Explanation:

Multiply both the numerators or denominators by 100 to eliminate the decimals

Simplify both fractions

Multiply the numerators and multiply the denominators and simplify the fraction by dividing both the numerator and denominator by 5.

Example Question #1 : Decimals With Fractions

 If can equal which of the following?

Possible Answers:

None of the other answer choices are correct

Correct answer:

Explanation:

Convert all of the fractions to decimals. Thus, x is contained within the range of 0.33 < x < 0.76. The answers choices become 1/4 = 0.25, 4/12 = 0.33, 2/5 = 0.4, and 5/16 = 0.3125, respectively.  Therefore, the only answer which is within the desired range is 2/5.

Example Question #1 : How To Find The Amount Of Rational Numbers Between Two Numbers

Two numbers have a greatest common divisor of 4 and a least common multiple of 40.  How many different pairs of numbers are there that satisfy these properties?

Possible Answers:

Correct answer:

Explanation:

The greatest common divisor is 4. This means that both numbers must be divisible by 4.  Furthermore, the least common multiple is 40, so both must divide 40.

The prime factorization of 40 is .  For a number to divide 40, it must therefore be composed of (at most) three 2's and one 5.  Because  divides both numbers, we also know that they must both have at least two 2's.

Now each number will have either two or three 2's and zero or one 5's.  However, we also know that they can't both have three 2's, (since then the greatest common divisor would have three 2's as well).  Similarly, only one can have a 5. 

In essence, our problem becomes one of choice.  We have 2 places with value 4.  We choose to give a 5 to one of the two. We then give a 2 to one of the two. If we give a 5 and a 2 to the same side, we end up with  and 4. If we give a 5 to one and a 2 to the other, we end up with  and .

Thus our two pairs are:

4,40 and 8,20

Example Question #1 : Compound Fractions

4/5 + 7/3 + 9/30 = ?

Possible Answers:

103 / 30

20 / 30

80 / 30

20 / 38

30 / 100

Correct answer:

103 / 30

Explanation:

To add fractions you must first find the lease common denominator, that is, a number that all of the denominators (the bottom number) can divide into.

In this case, 5, 3, and 30, both 5 and 3 divide successfully into 30, so 30 is the least common denominator. 

Now divide each smaller denominator into thirty.  Then multiple the answer by the top number:

5/30 = 6

Therefore 4/5 = 4*6 / 5*6 = 24/30

3/30 = 10

Therefore 7*10 / 3*10 = 70/30

Then add all the numerators together:

24/30 + 70/30 +9/30 = (24+70+9)/30 = 103 / 30

Example Question #2 : Compound Fractions

The student body of a high school is 1/4 boys, and 2/3 of the boys are seniors. If 1/18 of the senior boys were accepted into Harvard, which of the following could be the total number of students in the class?

Possible Answers:

15

90

108

54

148

Correct answer:

108

Explanation:

For this problem it would be easier to choose one of the answers and go from there. 108 works because 1/4 of 108 is 27 then 2/3 of 27 is 18 and 1/18 of 18 is 1, which makes this answer possible.

The other answers come out with a remainders that make no sense, since a fractional part of a person cannot have been accepted to a school.

Example Question #2 : How To Find A Solution To A Compound Fraction

Compute:

Possible Answers:

Correct answer:

Explanation:

Rewrite each fraction into an improper fraction.

The common denominator is 16.

The correct answer is:  

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