(UTC) 

  
 "Obsolete" has clear definitions. Slide rules had not fallen into disuse by 1973. Electronic calculators had not become household items and were uncommon among lower middle income people, and a novelty among those who could afford them. The general public was not spending hundreds of dollars for something they could do without, and it wasn't until the price hit $10 that it was accepted as an everyday item. In 1975, a deep discount store in NYC introduced a $10 calculator and there was a nonstop line to buy them. It was literally unheard of for a price that low before then. That is not of much relevance since it was far from the functional equivalent of a slide rule.  Schools still prohibited calculators since they offered an economic advantage/disadvantage to students. Prices did not drop to that point in the market as a whole until much later. An HP-35 would have been needed for grade school tests, and one still cost in the hundreds of dollars. They were banned from the SAT and similar tests until much later. By the end of the 1970s, prices had dropped to the level that made calculators common consumer items, but they were still not well accepted by educational institutions.  

 I can talk from experience, which is certainly not good enough for an article, even if accurate. Likewise, the statements in the article regarding obsolescence need a citation. Wikipedia does not allow opinion and there's nothing suggesting that this is general or common knowledge.   20:43, 30 April 2010