The geometric mean of two numbers x and y is √(xy).
So, if the geometric mean of 3 and a is 9 =>
9 = √(3a)
=> 9^2 = 3a
=> a = 9^2 / 3
a = 81 / 3
a = 27
Answer: the value of a is 27.
Make a ratio and cross multiply
3 should be added to the tiles
Since it starts at 12 and is increasing by 5 each time, the 70th term will be;
12 + 5(70)
12 + 350
362
362 is the 70th term of the sequence.
