Explanation

Numbers in order: 5, 7, 12, 18, 20

Middle value (3rd number) = 12

Explanation

To determine the selling price, we can use the formula:

Selling Price = Cost of Goods Sold (COGS) + Gross Profit

In this case,

the COGS is RS 120

and the gross profit is RS 80.

So, the selling price would be:

Selling Price = RS 120 + RS 80

Selling Price = RS 200

Explanation

Step 1: Let's denote the two numbers as x and y.
We have two equations:

1. x + y = 28

2. x - y = 4

Step 2: Solve the system of equations.
Adding the two equations eliminates y:
(x + y) + (x - y) = 28 + 4
2x = 32
Step 3: Solve for x.
x = 32 / 2
x = 16
Step 4: Solve for y.
Substitute x into one of the original equations:
16 + y = 28
y = 28 - 16
y = 12
Step 5: Identify the correct pair of numbers.
The numbers are 16 and 12.

Explanation

Sum of A,B,C,D = 45 * 4 = 180  

New average after E = 49 with 5 persons → Total sum = 49 * 5 = 245  

E's age = 245 - 180 = 65 years

Explanation

The mean proportional between two numbers a and b is √(ab).

So, √(2 × 8) = √16 = 4.