18 + x = 42
18 (miles traveled until gas was needed) + x (the miles traveled without needing gas) = 42 (total miles traveled)
M•8=24
Multiplication will become division when it changes side
m=24÷8
=A
k+26=61
Addition will become subtraction when it changes side
k=61-26
=B
<u>Answer:
</u>
The diameter of a sphere is 6ft 6in. The radius of sphere is 3 feet 3 inches.
<u>Solution:
</u>
Given that the diameter of sphere is 6 feet 6 inches.
We have to find the radius of the sphere.
The relation between diameter and radius of sphere is given as
![\text { diameter }=2 \times \text {radius}](https://tex.z-dn.net/?f=%5Ctext%20%7B%20diameter%20%7D%3D2%20%5Ctimes%20%5Ctext%20%7Bradius%7D)
Therefore, ![radius=\frac{\text {diameter}}{2}](https://tex.z-dn.net/?f=radius%3D%5Cfrac%7B%5Ctext%20%7Bdiameter%7D%7D%7B2%7D)
![radius=\frac{6 \text { feet } 6 \text { inches }}{2}](https://tex.z-dn.net/?f=radius%3D%5Cfrac%7B6%20%5Ctext%20%7B%20feet%20%7D%206%20%5Ctext%20%7B%20inches%20%7D%7D%7B2%7D)
Radius = 3 feet 3 inches.
Hence the radius of the sphere is 3 feet 3 inches.
We have an arithmetic progression:
an=number of item at row n
an=a₁+(n-1)d
d=common difference=an-a(n-1)=a₂-a₁=2-1=1
n=number of row
In this case:
an=1+(n-1)*1=n
The sum of an arithmetic serie is:
Sn=(a₁+an)n / 2
In this case:
a₁=1 (number of itms in the first row)
an=n (we have to calculate this before)
Sn=(1+n)n /2=(n+n²)/2
Therefore:
f(n)=Sn=number of items when we have n number of rows
f(n)=(n+n²)/2
Answer: f(n)=(n+n²)/2
To chek:
f(1)=(1+1²)/2=1
f(2)=(2+2²)/2=6/2=3
f(3)=(3+3²)/2=(3+9)/2=12/2=6
....