The variables x and y are directly proportional, and y=4 when x=3 . What is the value of y when x=15 ?

Using the proportionality concept, it is found that the value of y is 20 when x = 15.

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The variables x and y are directly proportional, which means that:

In which c is the constant of proportionality.

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y=4 when x=3

We use this to find the constant, thus:

Thus:

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When x = 15.

The value of y is 20 when x = 15.

A similar problem is given at link

lockers 1, 4, 9, 16, 25, 40, and 49 are open

i ran through it by the other answer is wrong

6x = 48

i hope this . 6 cards each and a total of $48. dvide each side by 6 and you will have your answer.