The median is the middle of your data when it is arranged in order.
Since you have 9 data points, the median will be the 5th value.
Your data in numerical order would be:
50 50 52 53 54 55 55 55 57
Therefore, the median is 54mm
If the series is made up of numbers in an arithmetic progression, you have

where

is the first term and

is the common difference between terms.
Since the last term in the series is

, you have

Solve the system

and you'll find that the first term is

(with

).
Answer:
If there are 24 green grapes, then there would be 32 black grapes!
Step-by-step explanation:
First, identify what you know.
1) In a bowl of fruit, there are green grapes, and black grapes.
2) The ratio of green grapes to black grapes is 3:4
3) There are 24 green grapes
Simply divide 4 by 3!
4/3 = 1.3
24 x 1.3 = 32
Hope this helps! :)