Verify if (3·8+5)/(4+3·8) = 5/4: Fraction Simplification Check

Determine whether the simplification below is correct:

38+54+38=54 \frac{3\cdot8+5}{4+3\cdot8}=\frac{5}{4}

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Determine if the reduction is correct
00:04 Let's calculate the products
00:22 Let's calculate the sums
00:31 Let's compare the expressions
00:35 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Determine whether the simplification below is correct:

38+54+38=54 \frac{3\cdot8+5}{4+3\cdot8}=\frac{5}{4}

2

Step-by-step solution

In this question we are asked whether we can "reduce" the expression on the left side.

In order to achieve this, first, let's numerically simplify the expression on the left side and calculate the value of the fraction in order to see if we obtain the same fraction (or its equivalent) that is on the right side:

38+54+38=24+54+24=2928 \frac{3\cdot8+5}{4+3\cdot8} =\\ \frac{24+5}{4+24}=\\ \frac{29}{28}

as shown below:

38+54+38?542928?54 \frac{3\cdot8+5}{4+3\cdot8}\stackrel{?}{\rightarrow }\frac{5}{4} \\ \downarrow\\ \frac{29}{28}\stackrel{?}{\rightarrow }\frac{5}{4}

Now we need to determine if the fractions are equivalent. For this we note that the denominator of the fraction on the right side, the number 28, is a whole multiple of the denominator of the fraction on the left side, 4, this whole multiple is the number 7 given that:

47=28 4\cdot7=28

Therefore we will expand the fraction on the right side, this we will do by multiplying both the numerator and denominator by 7. This is an operation that will not change the value of the fraction, given that it is equivalent to multiplying the fraction by 1. An operation that never changes the value of the number, as will be demonstrated in the following calculation:

54=541=5477=5747=3528 \frac{5}{4} =\\ \frac{5}{4} \cdot1=\\ \frac{5}{4} \cdot\frac{7}{7}=\\ \frac{5\cdot7}{4\cdot7}=\\ \frac{35}{28}

We therefore obtain the following:

2928?542928?3528 \frac{29}{28}\stackrel{?}{\rightarrow }\frac{5}{4} \\ \downarrow\\ \frac{29}{28}\stackrel{?}{\rightarrow }\frac{35}{28}

Now that the denominators of the fractions on the right and left sides are identical, we can determine that the fractions are different from each other since:

2935 29\neq35

and therefore the expression on the left and the expression on the right are not identical,

Meaning:

38+54+38=2930↛!54 \frac{3\cdot8+5}{4+3\cdot8}=\frac{29}{30}\stackrel{!}{\not{\rightarrow} }\frac{5}{4}

In other words - the reduction operation of the multiplication factor 38 3\cdot8 is incorrect.

Therefore the correct answer is answer B.

3

Final Answer

Incorrect

Practice Quiz

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Determine if the simplification below is correct:

\( \frac{4\cdot8}{4}=\frac{1}{8} \)

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