The change c of a telephone company is partly constant and partly varies as the number of units of call u. The cost of 90units is 1120 and the cost of 120unit is1216.find a formula that connects c and u.find c when u is 150units
c = ku + b
when u=90,c=120
1120 = 90k + b
when u=120, c=1216
1216 = 120k + b
subtract: 30k =96
k = 96/30= 16/5
go back into 1120 = 90k + b to find b
then form your equation,
so if u = 150 , c = .....
Nonsense this is rubbish everyone don't do this nonsense the person is showing. ugh
Female
To find a formula that connects the change in cost, c, with the number of units of call, u, we can set up a system of equations using the given information.
Let's define c1 as the constant part of the change in cost, and c2 as the part that varies with the number of units. We can now set up the equations:
For 90 units:
1120 = c1 + 90c2 ...(Equation 1)
For 120 units:
1216 = c1 + 120c2 ...(Equation 2)
Now, we have a system of two equations. To solve for c1 and c2, we can use various methods such as substitution or elimination.
Let's use the elimination method to solve this system:
Multiply Equation 1 by 120 and Equation 2 by 90 to eliminate c1:
(120)(1120) = (120)(c1) + (120)(90c2)
(90)(1216) = (90)(c1) + (90)(120c2)
This simplifies to:
134400 = 120c1 + 10800c2 ...(Equation 3)
109440 = 90c1 + 10800c2 ...(Equation 4)
Now, subtract Equation 4 from Equation 3 to eliminate c2:
134400 - 109440 = 120c1 - 90c1
24960 = 30c1
Dividing both sides by 30 gives us:
c1 = 832
Now that we know c1, we can substitute it back into Equation 4 to solve for c2:
109440 = 90(832) + 10800c2
109440 = 74880 + 10800c2
34560 = 10800c2
Dividing both sides by 10800 gives us:
c2 = 3.2
So, the formula that connects the change in cost, c, and the number of units of call, u, is:
c = 832 + 3.2u
To find c when u is 150 units, substitute u = 150 into the formula:
c = 832 + 3.2(150)
c = 832 + 480
c = 1312
Therefore, when u is 150 units, c is 1312.