Solve ACT Word Problem: Find Value of x

In summary, the larger of two numbers exceeds twice the smaller number by 8. The sum of twice the larger and 3 times the smaller number is 65. The correct equation to determine the value of the smaller number, x, is 2(2x+8)+3x=65 (option D). The mistake in the original attempt was not adding the 8 to the other side of the equation to show that y was greater than 2x by 8.
  • #1
down to earth
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I'm studying for the ACT and this was one of the practice test problems. The book does offer an explanation for how to get the answer but it isn't very detailed and I still don't know what I'm doing wrong.

Homework Statement


The larger of two numbers exceeds twice the smaller number by ##8##. The sum of twice the larger and ##3## times the smaller number is ##65##. If ##x## is the smaller number, which equation below determines the correct value of ##x##?

A. ##3(2x+8)+2x=65##
B. ##3(2x-8)+2x=65##
C. ##(4x+8)+3x=65##
D. ##2(2x+8)+3x=65##
E. ##2(2x-8)+3x=65##​

(According to the book, the correct answer is D.)

2. Homework Equations

To be consistent with the book, I'll let the larger number be ##y##, and the smaller number be ##x##.

The Attempt at a Solution


Taking this one step at a time:

The larger of two numbers exceeds twice the smaller number by ##8##.
I think this translates into ##y+8=2x##.

The sum of twice the larger and ##3## times the smaller number is ##65##.
So this means that ##2y+3x=65##. Now, because they want the answer to be in terms of ##x##, I need to rewrite ##y## in terms of ##x## (which is ##y=2x-8##) and plug that into the formula.

Then it becomes ##2(2x-8)+3x=65##. This is answer option E, but apparently this is isn't the right answer.​

Please, look over my steps and see if you can spot what I missed. The correct answer, D, differs only by the sign inside the parenthesis. I don't see what I'm doing wrong, and I'm really confused as to how they got ##+8##. Thank you.
 
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  • #2
If ##y## exceeds ##2x## by ##8## then ##y = 2x + 8##.
 
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PeroK said:
If ##y## exceeds ##2x## by ##8## then ##y = 2x + 8##.

Ohh... so I must've messed up at the first step then. I think I see what I did wrong now: to show that ##y## was greater than ##2x## by ##8##, I should have added the 8 on the other side of the equation. Dumb mistake on my part. Thanks!
 

What is the process for solving an ACT word problem to find the value of x?

The first step is to carefully read the word problem and identify the given information and what is being asked for. Then, use the given information to set up an equation that can be solved for x. Next, solve the equation using appropriate mathematical operations. Finally, check the solution by plugging it back into the original equation.

How can I improve my skills in solving ACT word problems to find the value of x?

Practice is key in improving your skills in solving ACT word problems. You can also review and familiarize yourself with various mathematical concepts and formulas that are commonly used in ACT word problems. Additionally, understanding the language and context of the word problem is crucial in identifying the given information and determining the appropriate equation to use.

What should I do if I get stuck on a difficult ACT word problem to find the value of x?

If you get stuck on a difficult ACT word problem, take a step back and review the given information and what is being asked for. It may also help to work backwards from the answer choices or ask for clarification from a teacher or tutor. If all else fails, move on to the next problem and come back to it later with a fresh perspective.

Are there any common mistakes to avoid when solving ACT word problems to find the value of x?

One common mistake is misinterpreting the given information or the question being asked. Make sure to read the word problem carefully and underline key information. Another mistake is not using appropriate units of measurement or not paying attention to the context of the problem. Always double check your work and make sure your answer makes sense in the given scenario.

How can I check my work when solving an ACT word problem to find the value of x?

You can check your work by plugging your solution back into the original equation and making sure it satisfies the equation. You can also estimate the answer and see if your solution is within a reasonable range. Additionally, you can use a calculator to check your work, especially for more complex calculations.

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