Solution:
Formula for finding the sum of odd numbers:n^2
As we know n is nmbr of values
So UpTo 50 there must be 25 odd numbers .
n=25 if there is any kind of doubt so let me explain the odd numbers..
1,3,5,7,9,11,13,15,17,19,21,23,27,29,31,33,35,37,39,41,43,45,47,49
Now you can count these numbers.
So, I'm going to put the values in above formula.
n^2
25^2
625

Solution:
Formula : n(n+1)
Here n is equal to number of digits.
So we can find even nmbr UpTo 100 by dividing it with 2
100/2 =50
So, n=50
By putting the values in above formula
n(n+1)
50(50+1)
50(51)
2250

Solution:
250 X 4%
=250 X 4/100
=250 X 1/25
=250/25
=10Answer

Solution:
Loss=Cost price- selling price
=RS.4000-Rs.2500
=RS.1500
Loss percentage=(loss/cost price)X100
=(1500/4000)X100
Loss percentage=37.5%

Solution:
Here the cost price of 1 orange =Rs9/12
=Rs 0.75
Selling price of 1 orange=Rs 18/20
=Rs 0.90
There is profit , because selling price is higher than cost price in the above answers.
Now,
Profit percent=(profit/cost price)X100
=(0.9-0.75)X100
=15%

Solution:
Mean=Sum of All values/Number of values
Mean=(1+3+5+8+9+12+18)/7
Mean=56/7
Mean=8

Definition of mode=most frequent value in the data or most repeated value in given data is termed as mode.
So here we saw the value 3 is repeated more than other values.

Median=[(n+1)/2]th
Here n is equal to number of values.
Data in Array form:
2,4,6,8,10,12,13
So here n=7
By using formulA:
Median=[(7+1)/2]th
Median=8/2
Median=4th
Means 4th value in Array data is median our mediAn that is 8.

20%of 80
=80 X 20/100
=80 X 1/5
=80/5
=16