Which of the following is not the value of central tendency based on all the observations?

Which of the following is not the value of central tendency based on all the observations?

The geometric mean of squares of two positive integers is 10. The smallest possible sum of these two integers is

In an arithmetic progression (AP), the 9th term is 5 times the 2nd term and the 8th termis 1 more than 10 times the first term. What is the 4th term of the geometricprogression (GP) whose first term is the second term of AP and whose common ratiois equal to the common difference of AP?

If $$1^2+2^2+3^2+………+14^2=1015,$$​ then $$3^2+6^2+9^2+………..+42^2$$​ is equal to:

If the ratio of the $$11^{th}$$ term of an AP to its $$18^{th}$$ term is 2 : 3, find the ratio of the sum of its first five terms to the sum of its first 10 terms​

The value of 1 + 2 + 3 + ... + 30 + 31 + 30 + 29+...+3 + 2 + 1 = ?