You are given a math word problem and you are supposed to make use of mathematical concepts like probability, combinatorics, linear equations, sequences/series, or simple operators like addition, subtraction, division, or multiplication to answer the given question. Choose the best option from the 5 given options and report that option.

Question: If x persons take y days to complete z similar jobs, how long does it take y persons to complete 1 such job?

 Option A: z

 Option B: x

 Option C: x/y

 Option D: z/x

 Option E: x/z
Option E

Question: A certain car dealership offers its newest model in ten exterior and six interior colors. If the ten interior colors are identical to the ten exterior colors, and the dealership sells every pair of colors except those that would result in a car with an identically colored interior and exterior, how many different color combinations are possible?

 Option A: 45

 Option B: 81

 Option C: 90

 Option D: 10!/2!

 Option E: 36
Option E

Question: Lakshmi invested some money in 25% stock at 500.If Usha wants to invest in an equally good 50% stock ,he must purchase a stock worth of :

 Option A: Rs. 1000

 Option B: Rs. 1200

 Option C: Rs. 1300

 Option D: Rs. 1400

 Option E: Rs. 1500

Option A