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.

Q: Question: A certain sum earns simple interest of Rs. 800 in 2 years at a certain rate of interest. If the same sum earns compound interest of Rs.900in the same period of 2 years, What must be the rate of interest?

 Option A: 25%

 Option B: 10%

 Option C: 15%

 Option D: 20%

 Option E: 30%

A: Option A
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Q: Question: Car ‘X’ covers a distance of 385 kms in 7 hours and car ‘Y’ covers a distance of 715 kms in 13 hrs. What is the difference in the speed of the two cars?

 Option A: 2kms/hr

 Option B: 1km/hr

 Option C: 3kms/hr

 Option D: 5kms/hr

 Option E: None of these

A: Option E
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Q: Question: The average age of a group of 10 students was 20. The average age increased by 2 years when two new students joined the group. What is the average age of the two new students who joined the group?

 Option A: 22 years

 Option B: 30 years

 Option C: 32 years

 Option D: 44 years

 Option E: None of these

A:
Option C
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