Numbers Questions

Which of the following numbers is not a prime number?

The 7th and 12th term of an arithmetic progression are -15 and 5 respectively. What is the 16th term?

What is the sum of the first 12 terms of an arithmetic progression if the first term is -19 and last term is 36?

Which of the following numbers is completely divisible by 99?

What is the sum of all prime numbers between 60 and 80?

The co-ordinates of the centroid of a triangle ABC are (-1,-2) what are the co-ordinates of vertex C, if co-ordinates of A and B are (6,-4) and (-2,2) respectively?

If the 1st and the 3rd term of an arithmetic progression are -10 and -4, what is the 12th term?

Out of a group of three numbers, second is thrice of the first and also twice of the third. If the sum of the three numbers is 55 then find the largest number in the group.