Sorry, but I have to disagree with Cerza on both answers. 1. While both "por" and "para" are grammatically correct, the sentence would not make much sense with the word "para." "Por" in this case is really a shorter form of stating "por causa de." The school was closed BECAUSE of the work on the metro; not in furtherance of it. While it is arguable that the closing of the school was integral to the work in progress, the use of "para" would have an instrumental meaning. In other words, it would imply that closing the school contributed to the work in some material way... which in this case is impossible, and really doesn't make any sense. As you pointed out in your question, "por" tells your listener that you are about to state a reason... or, to put it more accurately, the causality. The work on the metro is the CAUSE of the school closing. Therefore, the correct way to express this is always going to be with the word "por". 2. The expression "tercera edad" (third age) is not based on dividing the human lifespan into any number equal fractions. It is an idiom. The "first age" refers to humans when they are children, and must be cared for by their parents. The "second age" begins when children become adults, form their own families, and care for children of their own. The "third age" begins when these adults become infirm, and now much be cared for by their children. There is no exact definition according to number of years, as clearly this has changed over time. People are now living longer and getting married later. "Tercera edad" is not really a legal term, and cannot be precisely defined. Different people in different countries would provide different answers as to exact age groups. Its all a matter of perception!

Hi dear Derek! So look here below: 1) The correct is this situation and phrase is to use "para". Because por o para must to be in accord with the next sustantive if it is in the plural or singular and pay atention on the gender of the next words after " por /para). Entonces/so: The correct is: Cierran una escuela para las obras del metro. ( main point: las obras= palabras están en el plural ) use para. Un otro ejemplo seria: Ellos cierran la puerta para que las personas no entren adentro de la casa). (They close the door for not people entering inside the house) Tu eres mi amigo por eso dejo que vengas a mi casa. ( You are my friend and for that I let you come to my house). ________________________ 2) You are total right: The expression " tercera edad" means as one percentage ( as you said 100 years into 4 equal parts = Fifty to Seventy years. In English would be ( Third age of a person). --------------------- I hope I helped you friend! Espero haberte ayudado , amigo! Best Regards!

哈哈，我觉得第二个问题很有意思 :p tercera edad 我们一般用，来表达你们中文的"老人"。是一个有礼貌一点的方法。这个关键很重要，因为中文的"老"，西班牙语翻viejo, 但是这个词, 说人的时候，我们西班牙人会觉得很没有礼貌。我小时候，我妈妈会对我说这句话 "viejos son los libros" (no las personas). 加油！看起来你的西语水平很不错！

Hi dear Derek! So look here below: 1) The correct is this situation and phrase is to use "para". Because por o para must to be in accord with the next sustantive if it is in the plural or singular and pay atention on the gender of the next words after " por /para). Entonces/so: The correct is: Cierran una escuela para las obras del metro. ( main point: las obras= palabras están en el plural ) use para. Un otro ejemplo seria: Ellos cierran la puerta para que las personas no entren adentro de la casa). (They close the door for not people entering inside the house) Tu eres mi amigo por eso dejo que vengas a mi casa. ( You are my friend and for that I let you come to my house). ________________________ 2) You are total right: The expression " tercera edad" means as one percentage ( as you said 100 years into 4 equal parts = Fifty to Seventy years. In English would be ( Third age of a person). --------------------- I hope I helped you friend! Espero haberte ayudado , amigo! Best Regards!