Question

if x varies directly y and x=4 when y=16. find y when x=9

Answer 1

Answer:

If

y

varies directly as

x

, then if

y

increases,

x

increases, and if

y

decreases,

x

decreases. We can express this idea very succinctly in mathematics by writing

y

=

k

x

. Where

k

is a constant. Using this equation and substituting the initial values we have:

y

=

k

x

9

=

k

⋅

4

So

k

=

9

4

Hence we can rewrite our general relationship more particularly in this case as

y

=

9

4

x

.

Using the second set of values and our specific equation we get:

y

=

9

4

⋅

16

So

y

=

36