Answer:
<em>There are 12 boys and 18 girls</em>
Step-by-step explanation:
<u>Equations</u>
There are 30 students in a class. Let's call:
x = number of boys
Since the sum of boys and girls is 30:
30 - x = number of girls
The ratio of boys to girls is 2:3, thus:
Crossing denominators:
3x = 2(30 - x)
Operating the parentheses:
3x = 60 - 2x
Adding 2x:
5x = 60
Dividing by 5:
x = 60/5 = 12
x = 12
There are 12 boys and 30-12=18 girls
Given:
The sum of two terms of GP is 6 and that of first four terms is
To find:
The sum of first six terms.
Solution:
We have,
Sum of first n terms of a GP is
...(i)
Putting n=2, we get
...(ii)
Putting n=4, we get
(Using (ii))
Divide both sides by 6.
Taking square root on both sides, we get
Case 1: If r is positive, then using (ii) we get
The sum of first 6 terms is
Case 2: If r is negative, then using (ii) we get
The sum of first 6 terms is
Therefore, the sum of the first six terms is 7.875.