[PS] Guitar Hero

Algebra I (Illinois Edition), Prentice Hall, a Pearson subsidiary.


Is there anything inherent to buying an electric guitar that would lead to that equation ever?

[via Ryan Buck]


A music store sells a copy of a deluxe electric guitar for $295. This is $30 more than 1/3 the cost of the deluxe electric guitar it is modeled after. What is the cost of the deluxe electric guitar?


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  1. “You bought a used deluxe electric guitar from an online store for $295, shipping included. The seller told you it was a great deal because he was selling it for just one third of the original selling price, plus thirty dollars to cover shipping. If that’s true, how much did the guitar originally cost?”

  2. I like Zeno’s version. It’s a reasonable application, and it also avoids the triple repetition of the awkward phrase “deluxe electric guitar.”

  3. The other real-life variant of this kind of problem is the small retail operation: “You bought widgets wholesale at $14.37 each. Your store’s standard retail mark-up is 150% above the wholesale price, and you want to round to the nearest $0.50 price point so you don’t have to deal with pennies. How much should you price each widget?” I did a lot of that math at various jobs…

  4. Worse to me, here, is the process in setting up and solving the problem. What’s presented by the text suggests that a student can only solve the problem by “relating” in the specific way dictated above (eventually writing an equation). But what happens when the words change, or the order of the information changes? Lots of kids seem to botch this type of problem when they’d be fine if the cost of the original guitar were given and they were asked to find the cost of the model…

    Nice job by Zeno of cleaning this up, and I shudder if kids end up thinking this is the type of work they might do at an actual music store.

  5. Zeno did do a good job cleaning up the problem. The only change I would make is the verb “told” in the second sentence. I think that “wrote” would be better because the transaction is taking place online. I know that this is picking nits.

  6. My biggest beef with the original problem is the flippant use of the commutative property of addition. If the problem was written $30 less than instead of $30 more than, the $30 would come AFTER the subtraction sign. I am thinking in an Algebra I class, the commutative property would have been discussed by now? Ideally, put the $30 after the operation, be it addition OR subtraction.

  7. I like Zeno’s suggestion, I’d just change the ending to “how much would you actually save over buying it new”.