Pre-Algebra : One-Step Equations with Decimals

Study concepts, example questions & explanations for Pre-Algebra

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Example Questions

Example Question #1 : One Step Equations With Decimals

Solve for \(\displaystyle x\):

\(\displaystyle 0.75x=9\)

Possible Answers:

\(\displaystyle 12\)

\(\displaystyle 21\)

\(\displaystyle 9.75\)

\(\displaystyle 6\)

Correct answer:

\(\displaystyle 12\)

Explanation:

The goal is to isolate the variable on one side.

\(\displaystyle 0.75x=9\)

Divide each side by \(\displaystyle 0.75\):

\(\displaystyle \frac{0.75x}{0.75}=\frac{9}{0.75 }\)

\(\displaystyle x=12\)

Example Question #2 : One Step Equations With Decimals

Solve for \(\displaystyle x\):

\(\displaystyle 9.25x=74\)

Possible Answers:

\(\displaystyle -4\)

\(\displaystyle 8\)

\(\displaystyle -8\)

\(\displaystyle 4\)

Correct answer:

\(\displaystyle 8\)

Explanation:

The goal is to isolate the variable on one side.

\(\displaystyle 9.25x=74\)

Divide each side by \(\displaystyle 9.25\):

\(\displaystyle \frac{9.25x}{9.25}=\frac{74}{9.25}\)

\(\displaystyle x=8\)

Example Question #1 : One Step Equations With Decimals

Solve for \(\displaystyle n\):
\(\displaystyle 1.05+n=3.72\)

Possible Answers:

\(\displaystyle n=4.77\)

\(\displaystyle n=3.54\)

\(\displaystyle n=3.91\)

\(\displaystyle n=2.67\)

Correct answer:

\(\displaystyle n=2.67\)

Explanation:

\(\displaystyle 1.05+n=3.72\)

\(\displaystyle 1.05+n-1.05=3.72-1.05\)

\(\displaystyle n=2.67\)

Example Question #3 : One Step Equations With Decimals

Solve for \(\displaystyle x\):

\(\displaystyle 1.75+x=4.2\)

Possible Answers:

\(\displaystyle x=2.4\)

\(\displaystyle x=5.95\)

\(\displaystyle x=2.45\)

\(\displaystyle x=7.35\)

Correct answer:

\(\displaystyle x=2.45\)

Explanation:

\(\displaystyle 1.75+x=4.2\)

Subtract 1.75 from both sides of the equation:

\(\displaystyle 1.75+x-1.75=4.2-1.75\)

\(\displaystyle x=2.45\)

Example Question #3 : One Step Equations With Decimals

Solve for \(\displaystyle x\):

\(\displaystyle \small .6x=6\)

Possible Answers:

\(\displaystyle \small 36\)

\(\displaystyle \small 8\)

\(\displaystyle \small 3.6\)

\(\displaystyle \small 1\)

\(\displaystyle \small 10\)

Correct answer:

\(\displaystyle \small 10\)

Explanation:

To isolate \(\displaystyle x\), we must divide both sides by .6:

\(\displaystyle \small \small \frac{.6x}{.6}=\frac{6}{.6}\)

\(\displaystyle \small 1x=10\)

\(\displaystyle \small x=10\)

Example Question #4 : One Step Equations With Decimals

Solve for \(\displaystyle x\):

\(\displaystyle \frac{x}{0.15} = 3\)

Possible Answers:

\(\displaystyle 3\)

\(\displaystyle 0.30\)

\(\displaystyle 0.15\)

\(\displaystyle 0.45\)

\(\displaystyle 3.45\)

Correct answer:

\(\displaystyle 0.45\)

Explanation:

The goal is to isolate the variable on one side.

\(\displaystyle \frac{x}{0.15} = 3\)

The opposite operation of division is multiplication, therefore , multiply each side by 0.15:

\(\displaystyle \frac{0.15x}{0.15} = 0.15\times 3\)

The left hand side can be reduced by recalling that anything divided by itself is equal to 1:

\(\displaystyle 1\times x = 0.15 \times 3\)

The identity law of multiplication takes effect and we get the solution as:

\(\displaystyle x = 0.45\)

Example Question #2 : One Step Equations With Decimals

Solve for \(\displaystyle x\):

\(\displaystyle x - 0.23 = 7.12\)

Possible Answers:

\(\displaystyle 7.35\)

\(\displaystyle 6.89\)

\(\displaystyle 7.36\)

\(\displaystyle 8.35\)

\(\displaystyle 30.96\)

Correct answer:

\(\displaystyle 7.35\)

Explanation:

The goal is to isolate the variable on one side.

\(\displaystyle x - 0.23 = 7.12\)

The opposite operation of subtraction is addition so add 0.23 to each side:

\(\displaystyle x - 0.23 + 0.23 = 7.12 + 0.23\)

Simplifying, we get the final solution:

\(\displaystyle x = 7.35\)

Example Question #3 : One Step Equations With Decimals

Solve for \(\displaystyle x\):

\(\displaystyle x - 1.94 = 2.06\)

Possible Answers:

\(\displaystyle 0.12\)

\(\displaystyle 1.12\)

\(\displaystyle 3\)

\(\displaystyle 5\)

\(\displaystyle 4\)

Correct answer:

\(\displaystyle 4\)

Explanation:

The goal is to isolate the variable on one side.

\(\displaystyle x - 1.94 = 2.06\)

The opposite operation of subtraction is addition so add 1.94 to each side:

\(\displaystyle x - 1.94 + 1.94 = 2.06 + 1.94\)

Simplifying, we get the final solution:

\(\displaystyle x = 4\)

Example Question #1 : One Step Equations With Decimals

Solve for \(\displaystyle x\):

\(\displaystyle x + 0.001 = -3\)

Possible Answers:

\(\displaystyle 3.001\)

\(\displaystyle 2.999\)

\(\displaystyle -3.01\)

\(\displaystyle -2.999\)

\(\displaystyle -3.001\)

Correct answer:

\(\displaystyle -3.001\)

Explanation:

The goal is to isolate the variable on one side.

\(\displaystyle x + 0.001 = -3\)

The opposite operation of addition is subtraction so subtract 0.001 from each side:

\(\displaystyle x + 0.001 - 0.001 = -3 - 0.001\)

Simplifying, we get the final solution:

\(\displaystyle x = -3.001\)

Example Question #5 : One Step Equations With Decimals

Solve for \(\displaystyle x\):

\(\displaystyle x + 8.11 = 0.002\)

Possible Answers:

\(\displaystyle 8.18\)

\(\displaystyle 8.112\)

\(\displaystyle 8.108\)

\(\displaystyle -8.18\)

\(\displaystyle -8.108\)

Correct answer:

\(\displaystyle -8.108\)

Explanation:

The goal is to isolate the variable on one side.

\(\displaystyle x + 8.11 = 0.002\)

The opposite operation of addition is subtraction so subtract 8.11 from each side:

\(\displaystyle x + 8.11 - 8.11 = 0.002 - 8.11\)

Simplifying, we get the final solution:

\(\displaystyle x = -8.108\)

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