The change for telephone calls, T,is partly constant and partly varies with the number n of unit of call.the bill for 420 unit of call is #806,while the bill for 200 unit is #410.find obtain the change per unit of call ,find a formular T

T = a+bn

a + 420b = 806
a + 200b = 410
subtract, and you get
220b = 396
b = 1.80
since that is the slope, it's also the unit rate per call.
now use that to find a, and then you have the formula for T

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Pls show workings

Well, isn't this a tricky question? Talking about telephone bills always reminds me of those endless customer service calls. But let me give it a go!

So, we know that the bill for 420 units of call is #806 and the bill for 200 units is #410. To find the change per unit of call, we need to determine the constant part and the varying part of the change, right?

Let's call the constant part "C" and the varying part "V." We can set up two equations based on the given information:

1) C + V * 420 = 806
2) C + V * 200 = 410

Now, let's do some math magic to solve this peculiar puzzle:

Subtracting equation 2 from equation 1, we have:
(C + V * 420) - (C + V * 200) = 806 - 410

Simplifying, we get:
V * 420 - V * 200 = 396

Rearranging, we have:
V * (420 - 200) = 396

Calculating further, we find:
V * 220 = 396

Finally, dividing both sides by 220, we discover:
V = 396 / 220

And simplifying this, the change per unit of call, T, is approximately:
T ≈ 1.8

So, the formula for change per unit of call would be:
T = 1.8

Voila! I hope my mathematical circus act managed to amuse you a bit. If you have any more questions or need further assistance, feel free to ask!

To find the change per unit of call, we can first find the constant part of the change (let's call it C) and the varying part of the change (let's call it V).

From the given information, we know that the bill for 420 units of call is ₦806 and the bill for 200 units is ₦410.

Let's set up two equations using these data:

Equation 1: C + V * 420 = 806

Equation 2: C + V * 200 = 410

Now, we can solve these equations simultaneously to find the values of C and V. Here's how:

Step 1: Subtract Equation 2 from Equation 1 to eliminate C:

(C + V * 420) - (C + V * 200) = 806 - 410

Simplifying, we get:

V * 420 - V * 200 = 396

Step 2: Combine like terms:

V * (420 - 200) = 396

V * 220 = 396

Step 3: Solve for V:

V = 396 / 220

V ≈ 1.8 (rounded to one decimal place)

Now that we have the value of V, we can substitute it back into either of the original equations to solve for C:

Using Equation 1:

C + 1.8 * 420 = 806

C + 756 = 806

C = 806 - 756

C = 50

So, the constant part of the change (C) is 50 and the varying part of the change (V) is approximately 1.8.

To obtain the formula T, which represents the change per unit of call, we combine the constant and varying parts:

T = C + V

T = 50 + 1.8

T = 51.8

Therefore, the formula for the change per unit of call is T = 51.8.