Problem: Elevator doors protect riders from falling into the shaft. The most common configuration is to have two panels that meet in the middle, and slide open laterally. In a cascading telescopic configuration (potentially allowing wider entryways within limited space), the doors roll on independent tracks so that while open, they are tucked behind one another, and while closed, they form cascading layers on one side. This can be configured so that two sets of such cascading doors operate like the center opening doors described above, allowing for a very wide elevator cab. In less expensive installations the elevator can also use one large "slab" door: a single panel door the width of the doorway that opens to the left or right laterally. Some buildings have elevators with the single door on the shaft way, and double cascading doors on the cab.
How do most elevator doors work?
The answer is the following: have two panels that meet in the middle, and slide open laterally

In contemporary society, adolescents also face some risks as their sexuality begins to transform. While some of these, such as emotional distress (fear of abuse or exploitation) and sexually transmitted infections/diseases (STIs/STDs), including HIV/AIDS, are not necessarily inherent to adolescence, others such as teenage pregnancy (through non-use or failure of contraceptives) are seen as social problems in most western societies. One in four sexually active teenagers will contract an STI. Adolescents in the United States often chose "anything but intercourse" for sexual activity because they mistakenly believe it reduces the risk of STIs. Across the country, clinicians report rising diagnoses of herpes and human papillomavirus (HPV), which can cause genital warts, and is now thought to affect 15 percent of the teen population. Girls 15 to 19 have higher rates of gonorrhea than any other age group. One-quarter of all new HIV cases occur in those under the age of 21. Multrine also states in her article that according to a March survey by the Kaiser Family Foundation, eighty-one percent of parents want schools to discuss the use of condoms and contraception with their children. They also believe students should be able to be tested for STIs. Furthermore, teachers want to address such topics with their students. But, although 9 in 10 sex education instructors across the country believe that students should be taught about contraceptives in school, over one quarter report receiving explicit instructions from school boards and administrators not to do so. According to anthropologist Margaret Mead, the turmoil found in adolescence in Western society has a cultural rather than a physical cause; they reported that societies where young women engaged in free sexual activity had no such adolescent turmoil.
What percentage of sexually active teenagers will contract an STI?
One in four

Input: Philadelphia
The average population density was 11,457 people per square mile (4,405.4/km). The Census reported that 1,468,623 people (96.2% of the population) lived in households, 38,007 (2.5%) lived in non-institutionalized group quarters, and 19,376 (1.3%) were institutionalized. In 2013, the city reported having 668,247 total housing units, down slightly from 670,171 housing units in 2010. As of 2013[update], 87 percent of housing units were occupied, while 13 percent were vacant, a slight change from 2010 where 89.5 percent of units were occupied, or 599,736 and 10.5 percent were vacant, or 70,435. Of the city's residents, 32 percent reported having no vehicles available while 23 percent had two or more vehicles available, as of 2013[update].

How many houses or apartments were there in 2010?
Output: 670,171

Input: Article: In June 1837 Chopin visited London incognito in the company of the piano manufacturer Camille Pleyel where he played at a musical soiree at the house of English piano maker James Broadwood. On his return to Paris, his association with Sand began in earnest, and by the end of June 1838 they had become lovers. Sand, who was six years older than the composer, and who had had a series of lovers, wrote at this time: "I must say I was confused and amazed at the effect this little creature had on me ... I have still not recovered from my astonishment, and if I were a proud person I should be feeling humiliated at having been carried away ..." The two spent a miserable winter on Majorca (8 November 1838 to 13 February 1839), where, together with Sand's two children, they had journeyed in the hope of improving the health of Chopin and that of Sand's 15-year-old son Maurice, and also to escape the threats of Sand's former lover Felicien Mallefille. After discovering that the couple were not married, the deeply traditional Catholic people of Majorca became inhospitable, making accommodation difficult to find. This compelled the group to take lodgings in a former Carthusian monastery in Valldemossa, which gave little shelter from the cold winter weather.

Now answer this question: How much older was George Sands than Chopin?

Output: six years

Article: Various American Idol alumni had success on various record charts around the world; in the U.S. they had achieved 345 number ones on the Billboard charts in its first ten years. According to Fred Bronson, author of books on the Billboard charts, no other entity has ever created as many hit-making artists and best-selling albums and singles. In 2007, American Idol alums accounted for 2.1% of all music sales. Its alumni have a massive impact on radio; in 2007, American Idol had become "a dominant force in radio" according to the president of the research company Mediabase which monitors radio stations Rich Meyer. By 2010, four winners each had more than a million radio spins, with Kelly Clarkson leading the field with over four million spins.

Question: Who authored books on Billboard charts?
Ans: Fred Bronson

Input: Josip Broz Tito
As the Communist Party was outlawed in Yugoslavia starting on 30 December 1920, Josip Broz took on many assumed names during his activity within the Party, including "Rudi", "Walter", and "Tito." Broz himself explains:

Starting in what year was the Communist Party outlawed in Yugoslavia?
Output:
1920