HOW TO SELECT A PRODUCT ONLINE?

On a online store X, a product costs 200 dollars and it has 15 positive reviews. Another online store Y features the same product for a price of 250 dollars with 32 positive reviews. Which one to buy?
Little Math:
Find the product of prices and reviews . Then take the square root of the answer. Do it for the both the stores.

For store X:
Square root of (200*15) = 54.77
For store Y:
Square root of (250* 32) = 89.44

89.44 is greater than 54.77. Hence go for the store Y. These numbers called geometric mean. This 'measure' is used to compare widely different values like 200 and 15. Average stand best for closely related numbers like 120, 125, 101.

SOME MORE USES OF GEOMETRIC MEAN
1. Making square out of rectangle:

Say, 18 cm and 2 cm are the sides of a rectangle. Find the geometric mean of them.
Square root of( 8*2) =6.
Now draw a square with 6 cm side. The rectangle and the square will have the same area.
In other words
18 * 2 =6*6

2. Making cube from cuboid:
Say, a cuboid has sides 10 *51.2 *8.
Take geometric mean. Here we have to take cube root. Since we have three numbers.
Cube root of(10 * 51.2 * 8) = 16.
If you build a cube with side 16 CM, then the cuboid and the cube will have the same volume.
In other words
10 *5 * 2 * 8 = 16*16*16.

We can extend the principle of geometric mean to any number of numbers. For example
G.M of 1,3,9,27,81
1*3*9*27*81 = 59049
5th root of 59049 =9
Since there are five numbers, we take 5th root. Now,
1*3*9*27*81 = 9*9*9*9*9

GM Definition: For n numbers; multiply them all together and then take the nth root.

UNITED NATIONS HUMAN DEVELOPMENT INDEX -HDI
It is "..... a summary measure of average achievement in key dimensions of human development; 1. a long and healthy life 2. being knowledgeable 3. have a decent standard of living. The HDI is the "geometric mean" of normalized indices for each of the three categories."

A simple "GM" has many many applications. Math is fun and useful.
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