The ratio of 11th term to 18th term of an ap is 2:3.Find the ratio of 5th term to the 21st term, also the ratio of the sum of the first 5 terms to the sum of the first 21 terms.
Problem : The ratio of 11th term to 18th term of an AP is 2:3.Find the ratio of 5th term to the 21st term, also the ratio of the sum of the first 5 terms to the sum of the first 21 terms. [1/3, 5/49]