ACT Math : ACT Math

Study concepts, example questions & explanations for ACT Math

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Example Questions

Example Question #12 : Squares

A square garden has an area of 64 square feet. If you add 3 feet to each side, what is the new perimeter of the garden?

Possible Answers:

20

25

121

32

44

Correct answer:

44

Explanation:

By finding the square root of the area of the garden, you find the length of one side, which is 8. We add 3 feet to this, giving us 11, then multiply this by 4 to get 44 feet for the perimeter.

Example Question #1 : How To Find The Perimeter Of A Square

The area of the shaded region of a square is 18. What is the perimeter of the square?

Possible Answers:

28

20

36

24

Correct answer:

24

Explanation:

The area of the shaded region, which covers half of the square is 18 meaning that the total area of the square is 18 x 2, or 36. The area of a square is equal to the length of one side squared. Since the square root of 36 is 6, the length of 1 side is 6. The perimeter is the length of 1 side times 4 or 6 x 4.

Example Question #162 : Quadrilaterals

The area of a square is \(\displaystyle 25 cm^{2}\).  If the square is enlarged by a factor of 2, what is the perimeter of the new square?

Possible Answers:

\(\displaystyle 75\ cm\)

\(\displaystyle 40\ cm\)

\(\displaystyle 100\ cm\)

\(\displaystyle 50\ cm\)

\(\displaystyle 80\ cm\)

Correct answer:

\(\displaystyle 40\ cm\)

Explanation:

The area of a square is given by \(\displaystyle A = s^{2}\) so we know the side is 5 cm.  Enlarging by a factor of two makes the new side 10 cm.  The perimeter is given by \(\displaystyle P = 4s\), so the perimeter of the new square is 40 cm.

Example Question #4 : How To Find The Perimeter Of A Square

The diagonal of a square has a length of 10 inches. What is the perimeter of the square in inches squared?

Possible Answers:

\(\displaystyle 5\sqrt{2}\)

\(\displaystyle 6\sqrt{2}\)

\(\displaystyle 20\sqrt{2}\)

\(\displaystyle 10\sqrt{2}\)

Correct answer:

\(\displaystyle 20\sqrt{2}\)

Explanation:

Using the Pythagorean Theorem, we can find the edge of a side to be √50, by 2a2=102. This can be reduced to 5√2. This can then be multiplied by 4 to find the perimeter. 

Example Question #3 : How To Find The Perimeter Of A Square

What is the perimeter of a square with an area of \(\displaystyle 36\)?

Possible Answers:

\(\displaystyle 24\)

\(\displaystyle 30\)

\(\displaystyle 36\)

\(\displaystyle 12\)

\(\displaystyle 16\)

Correct answer:

\(\displaystyle 24\)

Explanation:

1. Find the side lengths:

\(\displaystyle Area= (side)^{2}\)

\(\displaystyle 36=(side)^{2}\)

\(\displaystyle side=6\)

 

2. Use the side lengths to find the perimeter:

\(\displaystyle Perimeter= 4(side)\)

\(\displaystyle Perimeter=4(6)=24\)

Example Question #1 : How To Find The Perimeter Of A Square

Find the perimeter of a square whose area is \(\displaystyle 16\).

Possible Answers:

\(\displaystyle 32\)

\(\displaystyle 64\)

\(\displaystyle 16\)

\(\displaystyle 4\)

\(\displaystyle 8\)

Correct answer:

\(\displaystyle 16\)

Explanation:

To solve, you must first find the side length.

\(\displaystyle s=\sqrt{A}=\sqrt{16}=4\)

Then, you must multiply the side length by 4 since there are 4 sides. Thus,

\(\displaystyle P=4*4=16\)

In this case, volume and perimeter were the same numerical value, but this won't always be the case.

Example Question #21 : Squares

Find the perimeter of a square with side length \(\displaystyle 1\).

Possible Answers:

\(\displaystyle 16\)

\(\displaystyle 1\)

\(\displaystyle 4\)

\(\displaystyle 2\)

Correct answer:

\(\displaystyle 4\)

Explanation:

To find perimeter, simply multiply side length by \(\displaystyle 4\). Thus,

\(\displaystyle P=1\cdot 4=4\)

Example Question #171 : Quadrilaterals

The area of a square is \(\displaystyle 64\textup{ in}^2\), what is the perimeter of the square?

Possible Answers:

\(\displaystyle \textup{36in}\)

\(\displaystyle \textup{32in}\)

\(\displaystyle \textup{Not enough information is provided.}\)

\(\displaystyle \textup{16in}\)

\(\displaystyle 24in\)

Correct answer:

\(\displaystyle \textup{32in}\)

Explanation:

Since the sides of a square are all the same, the area of a square can be found by \(\displaystyle \textup{side}*\textup{side}=64\textup{in}^2.\) Therefore, the side of the square must be \(\displaystyle 8\textup{in}.\) The perimeter of a square can be found by adding up all of the four sides:  \(\displaystyle \textup{8in+8in+8in+8in=32in.}\)

Example Question #1 : How To Find The Length Of The Side Of A Square

If the area of the square is 100 square units, what is, in units, the length of one side of the square?

Possible Answers:

\(\displaystyle 10\)

\(\displaystyle 5\)

\(\displaystyle 20\)

\(\displaystyle 25\)

\(\displaystyle 50\)

Correct answer:

\(\displaystyle 10\)

Explanation:

\(\displaystyle Area = Length \times Length\)

\(\displaystyle 100 = (Length)^2\)

\(\displaystyle Length = \sqrt{100}=10\)

Example Question #2 : How To Find The Length Of The Side Of A Square

In Square \(\displaystyle SQUA\)\(\displaystyle SU = \sqrt{2x}\). Evaluate \(\displaystyle SQ\) in terms of \(\displaystyle x\).

Possible Answers:

\(\displaystyle x\)

\(\displaystyle \sqrt{x}\)

\(\displaystyle 2x\)

\(\displaystyle 2\sqrt{x}\)

\(\displaystyle x\sqrt{2}\)

Correct answer:

\(\displaystyle \sqrt{x}\)

Explanation:

If diagonal \(\displaystyle \overline{SU}\) of Square \(\displaystyle SQUA\) is constructed, then \(\displaystyle \bigtriangleup SQU\) is a 45-45-90 triangle with hypotenuse \(\displaystyle SU = \sqrt{2x}\). By the 45-45-90 Theorem, the sidelength \(\displaystyle SQ\) can be calculated as follows:

\(\displaystyle SQ = \frac{SU}{\sqrt{2}} = \frac{\sqrt{2x}}{\sqrt{2}} = \sqrt{\frac{2x}{2}} = \sqrt{x}\).

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