The value of y is directly proportional to the value of x. If y=35 when x=140, what is the value of y when x=70?

Question

The value of y is directly proportional to the value of x. If y=35 when x=140, what is the value of y when x=70?

Answer 1

• "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 = 35 when X=140 means 35 = 140K
• K = 35/140 = 0.25
• Now that we know the value of K, we can use it to calculate the value of Y when X=70 
• Y = (0.25)(70) = 17.5