What is the value of s in the equation 1/2 + 2/5s = s - 3/4?

  • MHB
  • Thread starter EngineerJay
  • Start date
  • Tags
    Sat
In summary, the conversation involved solving an equation on Khan Academy and someone asking for help understanding a specific step. They were advised to multiply by the least common multiple of the denominators to clear them away and make the equation easier to solve. The final answer was found to be s = 25/12.
  • #1
EngineerJay
3
0
Hey everyone was having trouble solving this on Khan academy. The way they got the answer made no sense what so ever so hoping anyone here can help.

If 1/2 + 2/5s = s - 3/4, what is the value of s?
 
Mathematics news on Phys.org
  • #2
EngineerJay said:
[tex]
\text{Solve for }s:\;\;\tfrac{1}{2} + \tfrac{2}{5}s \;=\; s - \tfrac{3}{4}[/tex]

[tex]\begin{array}{ccc}\text{Multiply by 20:} & 10 + 8s \;=\;20s - 15 \\
\text{Simplify:} & 12s \;=\;25 \\
\text{Therefore:} & s \;=\;\frac{25}{12}
\end{array}[/tex]
 
  • #3
Okay so why did you multiply by 20? And how exactly?
 
  • #4
Since 20 is the least common multiple of 2, 4 and 5, multiplying by 20 clears away the denominators of the fractions, like this:

$$\dfrac12 + \dfrac{2}{5}s = s - \dfrac34$$

Multiply each side by 20:

$$20\left(\dfrac12 + \dfrac{2}{5}s\right) = 20\left(s - \dfrac34\right)$$

Expand:

$$20\cdot\dfrac12 + 20\cdot\dfrac{2}{5}s = 20s - 20\cdot\dfrac34$$

Evaluate:

$$10+8s=20s-15\implies s=\dfrac{25}{12}$$
 
  • #5
Wow thanks for the help! Now that I know I should of found the lcm of 2, 4 and 5 I feel some type of way(Giggle)! Again Thank you.
 

FAQ: What is the value of s in the equation 1/2 + 2/5s = s - 3/4?

What is "SAT Trouble"?

"SAT Trouble" refers to the difficulties and challenges that students may face while preparing for and taking the SAT (Scholastic Aptitude Test). This standardized test is commonly used by colleges and universities in the United States as part of their admissions process.

Why is the SAT important?

The SAT is important because it is used by many colleges and universities as a factor in their admissions decisions. A high score on the SAT can increase a student's chances of being accepted into their desired college or university. Additionally, some scholarships and financial aid opportunities may also consider a student's SAT score.

What are some common challenges students face when taking the SAT?

Some common challenges students face when taking the SAT include time management, test anxiety, difficulty with certain sections or types of questions, and lack of preparation or understanding of the test format and content.

How can students prepare for the SAT?

Students can prepare for the SAT by familiarizing themselves with the test format and content, practicing with sample questions and full-length practice tests, and seeking help from tutors or test prep courses if needed. It is also important for students to prioritize their time and manage their stress levels during the preparation process.

Are there any alternative options to the SAT for college admissions?

Yes, there are alternative options to the SAT for college admissions. Some colleges and universities have made the SAT optional or have adopted their own standardized tests. Additionally, some colleges and universities consider other factors such as GPA, extracurricular activities, and essays in their admissions decisions.

Similar threads

Replies
4
Views
2K
Replies
3
Views
3K
Replies
1
Views
905
Replies
2
Views
1K
Replies
10
Views
2K
Replies
2
Views
1K
Replies
2
Views
1K
Back
Top