Question

The value of 

y
is directly proportional to the value of 
x
.
x
.
if 
y
=
42
y
=
42
when 
x
=
84
,
x
=
84
,
what is the value of 
y
y
when 
x
=
35
x
=
35

Answer 1

y = 17.5

Explanation:

Given that y is directly proportional to x then the equation relating them is

y = kx ← k is the constant of proportion

To find k use the condition y = 42 when x = 84, then

42 = 84k ( divide both sides by 84 )

0.5 = k

y = 0.5x ← equation of proportion

When x = 35, then

y = 0.5 × 35 = 17.5