ACT Math : Exponents

Study concepts, example questions & explanations for ACT Math

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Example Questions

Example Question #171 : Exponents

Converting exponents to rational numbers often allows for faster simplification of those numbers.

Which of the following is incorrect? Convert exponents to rational numbers.

Possible Answers:

Correct answer:

Explanation:

To identify which answer is incorrect we need to do each of the conversions.

First lets look at 

.

Therefore this conversion is true.

Next lets look at . For this particular one we can recognize that anything raised to a zero power is just one therefore this conversion is true.

From here lets look at 

Thus

. Therefore this is an incorrect conversion and thus our answer.

Example Question #172 : Exponents

Sometimes, seeing rational numbers makes it easier to understand an equation.

Convert the following into a rational number or numbers:

Possible Answers:

Correct answer:

Explanation:

The rule for converting exponents to rational numbers is: .

Even with this, it is easier to work the problem as far as we can with exponents, then switch to rational expression when we run out of room:

At last, we convert, and obtain .

Thus, 

.

Example Question #1 : How To Use Scientific Notation

What is the sum of the solutions of the equation x2-2x-8=0?

 

Possible Answers:

-10

-2

2

-6

6

Correct answer:

2

Explanation:

The equation factors to (x-4)(x+2)=0, indicating that the roots are x=-2,4. The sum of these two roots is 2.

 

 

Example Question #1 : How To Use Scientific Notation

What is the number 350,000,000 in scientific notation?

Possible Answers:

3.5 x 108

3.5 x 109

3.5 x 106

3.5 x 105

3.5 x 107

Correct answer:

3.5 x 108

Explanation:

350,000,000 = 3.5 x 108 (exponent is equal to the number of decimal points shifted)

Example Question #3 : How To Use Scientific Notation

Given the equation 2xy + 4x² - y = 2x, if x = 2, what does y equal?

Possible Answers:

4

2

0

-4

Correct answer:

-4

Explanation:

We plug in the value given for x and solve for y. 

2xy + 4x² - y = 2x

2(2)y + 4(2)² - y = 2(2)

4y + 4(4) - y = 4

4y - y + 16 = 4

3y = -12

y = -4

Example Question #1 : How To Use Scientific Notation

How do you express 657,800 in scientific notation?

Possible Answers:

65.78 × 104

65.78 × 103

65.78 × 106

6.578 × 104

6.578 × 103

Correct answer:

65.78 × 104

Explanation:

657800 = 6.578 × 105

OR

657800 = 65.78 × 104

Exponent on 10 is the number of decimal points over the number has shifted.

Example Question #5 : How To Use Scientific Notation

2 × 100 + 3 × 102 + 4 × 104 = ?

Possible Answers:

40,302

40,320

4,032

400,032

432

Correct answer:

40,302

Explanation:

2 × 100 + 3 × 102 + 4 × 104 =

2 + 300 + 40,000 = 40,302

Example Question #1 : How To Use Scientific Notation

Give this number in scientific notation:

Possible Answers:

Correct answer:

Explanation:

There are six zeros and two more number places, for a total of eight, so 125,000,000 is equivalent to .

Example Question #171 : Exponents

Simplify the following expression:

 

Possible Answers:

Correct answer:

Explanation:

 

 

Example Question #2 : Other Exponents

What is the number \dpi{100} \small 256,000,000,000 in scientific notation?

Possible Answers:

\dpi{100} \small 2.56\times 10^{11}

\dpi{100} \small 2.56\times 10^{10}

\dpi{100} \small 2.56\times 10^{12}

\dpi{100} \small 2.56\times 10^{13}

\dpi{100} \small 2.56\times 10^{9}

Correct answer:

\dpi{100} \small 2.56\times 10^{11}

Explanation:

\dpi{100} \small 256,000,000,000 = 2.56\times 10^{11} 

The exponent is equal to the number of decimal points shifted.

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