ACT Math : How to use scientific notation

Study concepts, example questions & explanations for ACT Math

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Example Questions

Example Question #1 : How To Use Scientific Notation

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

 

Possible Answers:

-2

-10

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 107

3.5 x 105

3.5 x 106

3.5 x 109

3.5 x 108

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 #2 : 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 : Other Exponents

How do you express 657,800 in scientific notation?

Possible Answers:

65.78 × 104

6.578 × 103

65.78 × 103

6.578 × 104

65.78 × 106

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 #2 : How To Use Scientific Notation

2 × 100 + 3 × 102 + 4 × 104 = ?

Possible Answers:

4,032

40,320

400,032

432

40,302

Correct answer:

40,302

Explanation:

2 × 100 + 3 × 102 + 4 × 104 =

2 + 300 + 40,000 = 40,302

Example Question #1 : Other Exponents

Give this number in scientific notation:

\displaystyle 125,000,000

Possible Answers:

\displaystyle 12.5\times 10^{10}

\displaystyle 1.25\times 10^{9}

\displaystyle 12.5\times 10^{8}

\displaystyle 1.25\times 10^{7}

\displaystyle 1.25\times 10^{8}

Correct answer:

\displaystyle 1.25\times 10^{8}

Explanation:

There are six zeros and two more number places, for a total of eight, so 125,000,000 is equivalent to \displaystyle 1.25 \times 10^{8}.

Example Question #2 : Other Exponents

Simplify the following expression:

\displaystyle (4(i^{2}-3))^{\frac{1}{2}}

 

Possible Answers:

\displaystyle 16

\displaystyle 4i

\displaystyle -4

\displaystyle 2i

Correct answer:

\displaystyle 4i

Explanation:

\displaystyle (4(i^{2}-3))^{\frac{1}{2}} =(4(-1-3))^{\frac{1}{2}} =(4(-4))^{\frac{1}{2}}

 \displaystyle =(-16))^{\frac{1}{2}}=\sqrt{-16}=\sqrt{(16)(-1)}=4i

 

Example Question #1 : How To Use Scientific Notation

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^{13}

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

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

\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.

Example Question #2 : How To Use Scientific Notation

Convert from scientific to decimal notation:

\displaystyle 2.3\times 10^{4}

Possible Answers:

\displaystyle 0.0023

\displaystyle 0.00023

\displaystyle 23,000

\displaystyle 230,000

\displaystyle 2300

Correct answer:

\displaystyle 23,000

Explanation:

In this case the exponent is positive hence you have to move the decimal point 4 places to the right from where it is in the problem giving us

\displaystyle 23,000

Example Question #4 : How To Use Scientific Notation

Convert from decimal to scientific notation:

 

\displaystyle 0.0000034

Possible Answers:

\displaystyle 3.4\times 10^{-6}

\displaystyle 3.4\times 10^{-5}

\displaystyle 3.4\times 10^{7}

\displaystyle 3.4\times 10^{-4}

\displaystyle 3.4\times 10^{6}

Correct answer:

\displaystyle 3.4\times 10^{-6}

Explanation:

In this case you have to move the decimal point 6 places to the right. When you move the decimal point to the right the exponent becomes negative.  Similarly when you move the decimal point to the left the exponent is positive.  Also, to the left of the decimal place there can be only one digit.

\displaystyle 3.4* 10^{-6}

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