Explanation:
Y is directly proportional to X" can be rewritten as a mathematical expression of the form Y = KX
"K" is the constant of proportionality and must be determined from the initial information.
If Y = 45 when X=140 means 45 = 140K
K = 45/140 = 0.32
Now that we know the value of K, we can use it to calculate the value of Y when X=70
Y = (0.32)(70) = 22.4