If you have to purchase an exam-approved graphing calculator for your student, you're probably going to experience sticker shock. They can run as much as $150.

Here's a few ways to save and look like a math genius:

New: Walmart has a an advanced function, exam approved Casio Graphing Calculator for $48.93. Make sure the calculator has USB port (this one does), which is important. Some cheaper models on the market don't have one. You're not going to do better than this price for a new device. Shipping is 97 cents.

Apps: Download the top-rated Graphing Calculator by Gabor Nagy App for iPod, iPad and iPhone from iTunes for $1.99. It was just updated at the end of July. Your student may not be able to use this during an exam or in class (check with your child's teacher on the school's policy), but its more convenient to tote around than the big, clunky device.

Used: Math teachers suggest you check out listings on CraigsList.org and eBay.com. There are loads of them being offered at a big discounts. You can pick up the top-rated Texas Instruments TI-83 or TI-84 for as little as $45.

Before you buy, check with your child's math teacher or school to find out about rules and requirements and what features are needed.

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