Based on the given variation, y does not vary directly with x and the constant of variation are 8, 3.2 and 1.25 respectively.
<h3>Variation</h3>
y = k × x
where,
k = constant of proportionality
y = -40
x = -5
y = k × x
-40 = k × -5
-40 = -5k
k = -40/-5
k = 8
when,
y = 8 and x = 2.5
y = k × x
8 = k × 2.5
8 = 2.5k
k = 8/2.5
k = 3.2
when,
y = 5 and x = 4
y = k × x
5 = k × 4
5 = 4k
k = 5/4
k = 1.25
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To find the incompleted portion of the test, convert the decimal to a percentage by moving the decimal two places to the right. .7 as a percentage is 70%. subtract 70% from 100%, giving you 30%. Juan has not completed 30% of his test, or 5 questions.
The answer to ur division problem would be 27.6785714286<span>
</span>
Let's assign variables
The time required to <span>wire a building: y
</span>
The number of electricians <span>to have done this job: x
</span>
<span>y varies inversely as x
so that:

where k is the proportional constant
To calculate the value of k, plug in the values of x and y:
x=7
y=4

Now, write down the relation between x and y:

"</span><span>how long would it have taken 3 electricians to have done the job?"
x=3
Let's find out y:

So it would take 9 hours and 20 minutes to have this job done.
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