Find the ratio in which rice at Rs.7.20 a kg be mixed with rice at Rs.5.80 a kg to produce a mixture worth Rs.6.30 a kg?  Choose the correct answer:	A) 5 : 9	B) 2 : 3	C) 3 : 4	D) 4 : 5	E) none of these

Rationale: "solution required ratio = 50 : 90 = 5 : 9 answer a"
Answer: A