It would take 10 years for the given sum of money be doubled at the given simple interest rate.
Step-by-step explanation:
A 10% interest would be added to the the principal amount after each year. So the interest would reach 100% i.e. equal to the principal amount in 10 years.
A ratio is written as x:y where x and y are numbers in there most simplified form. In the ratio 24:28 both numbers are divisible by four, so divide each side by four and you have your answer.