There are n-AM's between 1 and 31 such that 7th mean:(n-1) th mean =5:9 then find the value of n
d=31−1n+1=30n+1
According to the question a+7da+(n−1)d=5/9⇒4=5 n-68 30n+1⇒4n+4=150n−2040⇒n=14