{"product":{"product_id":"3540224947","title":"How to Solve It: Modern Heuristics","price":"86.93","image_url":"https://m.media-amazon.com/images/I/41VLdUQHbTL._SL500_.jpg","url":"https://www.amazon.com/dp/3540224947"},"comments":[{"body":"I must have been a bit unclear in my wording. One of the main reasons for my complaints is that I want a calculator that is faster and has a higher resolution. We both already agree, then, that the EX series is newer, faster, and has a higher resolution screen than the ES series. Anything I wrote on that subject is meant only to confirm those facts with hard evidence and to show more-precisely how much faster the EX series is than the ES series, rather than leaving the answer a vague \"faster\". It turns out the EX is about 5 times faster than the ES.\r\n\r\nAs a mathematics and computer science graduate who often tutors students ranging from fifth year elementary maths to linear algebra and number theory, I use almost all of the functions on the 115es plus at different points. I enjoy keeping my maths knowledge intact by doing some calculations or solutions on paper or in my head and using my calculator to confirm my results or tell me I'm wrong, which includes something as simple as finding the prime factorization of a somewhat large integer or finding the product of a series. Those are but two of many (literally hundreds, as mentioned in my post) examples of what the fx-115ES Plus can do that the US fx-991EX can't do at all. I can get around some of those by converting the products to sums but that's a huge extra step on my part and also hardly worth doing since those will take a very long time on the calculator. I like to go to the library on weekends and study [\"How to Solve It: Modern Heuristics\"](https://www.amazon.com/How-Solve-Heuristics-Zbigniew-Michalewicz/dp/3540224947), which covers various areas of maths, and getting through all tedious calculations by using my cheap scientific calculator or confirming the soundness of my more symbolic results by doing a few quick inexact calculations. That's why I would LOVE the fx-991EX to do all that my old fx-115ES Plus can do. I also hate worrying about the battery life of my graphing calculators and having to recharge them. I hardly have to worry if I've been doing tens of hours of calculations on my scientific calculator for weeks on end, but often have to get new batteries for my TI-89 or have to recharge any of the newer ones. I'm honestly really tired of always having to worry about recharging my mobile and other devices as well.\r\n\r\nI have a similar philosophy for other devices, like my MP3 player, the [SanDisk Clip+](https://www.amazon.com/SanDisk-Sansa-Player-Discontinued-Manufacturer/dp/B002MAPS6W). I got it when it was cheap, not $100 as it is now due to scarcity. After I switched its operating system to RockBox, which makes it able to play all sorts of audio files and added tons of functionality like a highly-customizable equalizer, I had a very simple device that could do everything I wanted. I don't care about fancy colors and album art or touchscreens on a simple audio player. All that stuff breaks and uses more power anyway. All I care about is that it's powerful enough to do all the real things I want it to do, not pointless fancy graphical things meant only for marketing purposes that are detrimental overall.","subreddit_name":"calculators","author":"ThrowdownTornado"}]}